Blood filtration systems

ABSTRACT

A blood filtration system can reduce the amount of plasma constituents (e.g., water and/or electrolytes) in the blood of the patient, and accordingly increase the hematocrit value of the patient. The blood filtration system (e.g., a controller, or the like) can determine a hematocrit value of a patient. The blood filtration system can determine a venous pressure of vasculature of a patient. The blood filtration system can compensate for pressure head in a component of a blood circuit (e.g., a withdrawal line of a catheter), for example to improve the accuracy of the venous pressure determination. The blood filtration system can determine one or more resistance characteristics of a blood circuit for the blood filtration system. The resistance characteristics can correspond to a resistance to a flow of blood through a component of the blood circuit.

CLAIM OF PRIORITY

This patent application claims the benefit of priority of Lerner et al.,U.S. Provisional Patent Application Ser. No. 62/787,106, titled “BLOODFILTRATION SYSTEMS,” filed on Dec. 31, 2018 (Attorney Docket No.4567.027PRV); and Lerner et al., U.S. Provisional Patent ApplicationSer. No. 62/787,090, titled “BLOOD FLOW ASSISTING PORTABLE ARM SUPPORT,”filed on Dec. 31, 2018 (Attorney Docket No. 4567.026PRV) the benefit ofpriority of each of which is claimed hereby, and each of which areincorporated by reference herein in its entirety.

CROSS-REFERENCE TO RELATED PATENT DOCUMENTS

This patent application is also related to the application titled “BLOODFLOW ASSISTING PORTABLE ARM SUPPORT” by Lerner et al., filed on Dec. 31,2018 (Attorney Docket No. 4567.026PRV), which is hereby incorporated byreference herein in its entirety.

TECHNICAL FIELD

This document pertains generally, but not by way of limitation, tomedical devices.

BACKGROUND

A blood filtration system can remove blood from the blood stream (e.g.,venous circulation) of a patient and separate plasma water andelectrolytes from erythrocytes (e.g., red blood cells) and other bloodconstituents by means of a filter. The system can convey the plasmawater to a reservoir (e.g., a bag) for disposal. The balance of theplasma water, the erythrocytes, and other blood constituents arereturned to the patient's blood stream. Once blood is withdrawn from theblood stream and makes contact with extracorporeal components of theblood filtration system (e.g., tubing, the filter, or the like), apotential exists for clots to form within the extracorporeal components,leading to an increase in resistance within the components (e.g., thefilter), and potentially clogging (e.g., occluding) the components.While not harmful to the patient, the increase in resistance or clottingcould necessitate replacement of one or more of the extracorporealcomponents.

SUMMARY

The hematocrit value in a patient is a ratio of the red blood cellvolume to the total volume of blood in a patient, where the total volumeof blood includes the red blood cell volume and the volume of plasma(including, but not limited to water, proteins, and electrolytes) in theblood of the patient. In some examples, a patient experiencingcongestive heart failure can have excess plasma volume, and accordinglya reduced hematocrit value. For instance, the patient can have excessplasma water that corresponding increases the plasma volume of thepatient (and lowers the hematocrit value of the patient). A bloodfiltration system can reduce the amount of plasma constituents (e.g.,water and/or electrolytes) in the blood of the patient, and accordinglyincrease the hematocrit value of the patient.

The present inventors have recognized, among other things, that aproblem to be solved can include improving the accuracy of a hematocritvalue determination (e.g., measurement, assessment, evaluation,computation, or the like). Additionally, the present inventors haverecognized, among other things, that a problem to be solved can includedetermining if a hematocrit value determination is affected by movementof a patient (e.g., when a patient transitions from a supine position toa standing position). Further, the present inventors have recognized,among other things, that a problem to be solved can include determiningthe amount of plasma remaining in the patient.

Still further, the present inventors have recognized, among otherthings, that a problem to be solved can include determining a rate ofremoving plasma constituents while maintaining preferred patientdiagnostic parameters (e.g., vital signs, for instance vascularresistance, venous pressure or the like). Still yet further, the presentinventors have recognized, among other things, that a problem to besolved can include determining when to cease removal of the plasmaconstituents from the blood stream to obtain a preferred hematocritvalue (e.g., euvolemia, or a preferred amount of blood in the patient)in the patient. Additionally, the present inventors have recognized,among other things, that a problem to be solved can include reducingclogging of the extracorporeal components of a blood filtration system.

The present subject matter can help provide a solution to this problem,such as by providing a blood filtration system. The blood filtrationsystem can reduce one or more plasma constituents in blood of a patient.The blood filtration system can include a variable-speed blood pump thatcan be configured to pump blood in a withdrawal line, through a filter,and into an infusion line. The withdrawal line and the infusion line canbe configured to couple with a catheter, and the catheter can beconfigured for insertion into a blood stream of the patient. Thewithdrawal line and the infusion line can be configured to couple withthe filter. The filter can be configured to reduce an amount of one ormore plasma constituents in blood flowing through the filter and providea filtrate fluid including the plasma constituents. The blood filtrationsystem can include a variable speed filtration pump that can beconfigured to extract the filtrate fluid from the filter.

The blood filtration system can include a controller includingprocessing circuitry. The controller can be configured to control thespeed of the blood pump to vary the flow rate of the blood through thefilter. Additionally, the controller can be configured to control thespeed of the filtration pump to vary the extraction rate of the filtratefluid from the filter. Further, the controller can be configured todetermine the venous pressure of the patient. Still further, thecontroller can be configured to provide a notification of the venouspressure of the patient (e.g., providing a notification on a display).In some examples, the blood filtration system can determine the venouspressure of the patient by controlling the speed of the blood pump tostop the blood pump. The blood filtration system can determine thevenous pressure of the patient because the blood filtration system canbe in communication with the blood stream of the patient.

Additionally, the controller can be configured to determine a hematocritvalue of the patient. In an example, determining the hematocrit value ofthe patient includes controlling the speed of the blood pump and settingthe flow rate of blood through the filter. Controlling the speed of theblood pump can improve the accuracy of the hematocrit valuedetermination. For instance, the hematocrit value determination by anoptical hematocrit sensor can be affected by the flow rate of bloodthrough the filter. In this example, the speed of the blood pump canvary, and the determined hematocrit value of the patient can varyaccording to the speed of the blood pump. Accordingly, measuring thehematocrit value with the blood pump at a consistent speed can improvethe accuracy of the hematocrit value determination.

Further, the controller can be configured to determine if movement ofthe patient from an initial position affects the determined hematocritvalue of the patient. For instance, a sensor can be configured tomonitor movement of the patient relative to the initial position of thepatient. The controller can be configured to provide a notification ifthe hematocrit determination is affected by the movement of the patient.In an example, the controller can provide a notification (e.g., on adisplay) with a timer since the patient moved in a way that affected thehematocrit value determination. In another example, the controller canrefrain from providing a notification of the hematocrit value when thehematocrit value is affected by movement of the patient (e.g., byrefraining from displaying the movement-affected hematocrit value on adisplay). Accordingly, the blood filtration system can provideadditional information (e.g., to a healthcare provider) that thehematocrit value of the patient has been affected by movement of thepatient.

Further, the controller can be configured to change a filtration ratethat the one or more plasma constituents are extracted from the filter.For instance, the controller can control a speed of a filtration pump tochange the extraction rate of the plasma constituents from the filter.The filtration rate can be changed (e.g., increased or decreased) aspecified of amount, and the controller can determine the hematocritvalue of the patient (or a rate of change of the hematocrit value ofthe) before and after the change in filtration rate. In some examples,the amount of change of the filtration rate and the determinedhematocrit values before and after the change in filtration rate can beused to determine the amount of plasma constituents remaining in apatient. Determining the amount of plasma constituents remaining in thepatient can be used to determine how much of the plasma constituents theblood filtration system should extract from the patient.

Still further, the controller can be configured to control a speed ofone or more pumps to adjust a filtration fraction of the system. Thefiltration fraction can include a ratio of a filtration rate (e.g., arate that one or more plasma constituents is extracted from the filter)to a blood flow rate through the filter. The controller can vary thespeed of the one or more pumps (e.g., the filtration pump, the bloodpump, or the like) to adjust the filtration fraction. Additionally, thecontroller can be configured to determine the hematocrit value, and cancompare the hematocrit value to a hematocrit threshold. The controllercan be configured to maintain the filtration fraction, for instance whenthe hematocrit value equals the hematocrit threshold. Further, thecontroller can be configured to adjust the filtration fraction, forinstance if the hematocrit value exceeds, or declines below, thehematocrit threshold. In some examples, the hematocrit threshold is arange of hematocrit values (e.g., 45 percent to 55 percent). Controllingthe filtration fraction can be used to control the rate of removingplasma constituents while maintaining preferred patient diagnosticparameters. Additionally, controlling the filtration fraction can beused to reduce clogging of the extracorporeal components of a bloodfiltration system. For instance, when the hematocrit value is high(e.g., greater than 50 percent) the filter can have an increasedprobability of clogging). In some examples, the filtration fraction canbe reduced (e.g., filtration rate reduced, blood flow rate increased, ora combination thereof) to reduce the probability of clogging in thefilter.

This summary is intended to provide a summary of subject matter of thepresent patent application. It is not intended to provide an exclusiveor exhaustive explanation of the invention. The detailed description isincluded to provide further information about the present patentapplication.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralscan describe similar components in different views. Like numerals havingdifferent letter suffixes can represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 shows a schematic view of an example of a first blood filtrationsystem.

FIG. 2 shows a schematic view of an example of a second blood filtrationsystem.

FIG. 3 shows a flowchart of a first method for preserving a filter for ablood filtration system.

FIGS. 4A-4H show a schematic view of an example of a third bloodfiltration system.

FIG. 5 shows a schematic view of a fourth blood filtration system.

FIG. 6 shows a flowchart for a second method for preserving a filter fora blood filtration system.

FIG. 7 shows a schematic view of a fifth blood filtration system.

FIGS. 8A-8B shows a schematic view of a sixth blood filtration system.

FIG. 9 shows a schematic view of a seventh blood filtration system.

FIG. 10 shows a schematic view of an eighth blood filtration system.

FIGS. 11A-11B are photographs of line protectors for a blood filtrationsystem.

FIG. 12 is a block diagram illustrating an example of a machine uponwhich one or more embodiments can be implemented.

FIG. 13 shows a graph of a filtration fraction of a blood filtrationsystem versus a hematocrit level of a patient.

FIG. 14 shows a method for determining venous pressure of a patient witha blood filtration system.

DETAILED DESCRIPTION

FIG. 1 shows a schematic view of an example of a first blood filtrationsystem 100. The blood filtration system 100 can be configured to reduceone or more plasma constituents (e.g., water, proteins, electrolytes, orthe like) in blood of a patient. The blood filtration system 100 caninclude a controller 102. The controller 102 can include processingcircuitry, for instance an integrated circuit. As described herein, thecontroller 102 can be configured to control one or more components ofthe blood filtrations system 100.

The blood filtration system 100 can include a withdrawal line 104 andcan include an infusion line 106. The lines 104, 106 can be configuredto couple with a catheter 108, and the lines 104, 106 can transmit bloodwithin the blood filtration system 100. In an example, the catheter 108can be inserted into a blood stream of the patient, for instance thecatheter 108 can be inserted into a basilic vein, cephalic vein,brachial vein, the axillary vein, the subclavian vein, thebrachiocephalic vein, or the like. Blood can flow into the catheter 108,into the withdrawal line 104, through other components of the system100, through the infusion line 106, into the catheter 108, and back intothe blood stream of the patient. The line 104 can be separate from theline 106. The lines 104, 106 can be in communication with the catheter108. For example, the catheter 108 can include one or more lumens, forexample a withdrawal lumen in communication with the line 104 and aninfusion lumen in communication with the line 106.

The lines 104, 106 can be configured to couple with a filter 110, forinstance the lines 104, 106 can include one or more fittings thatfacilitate coupling the lines 104, 106 with the filter 110. In anexample, the withdrawal line 104 can couple with a filter inlet port111A, and the infusion line 106 can couple with a filter outlet port111B. The filter 110 can be configured to reduce an amount of one ormore plasma constituents (e.g., water, electrolytes, or the like) inblood flowing through the filter 110 and provide a filtrate fluidincluding the one or more plasma constituents. As described herein,blood can flow through the lines 104, 106 to and from the catheter 108.The lines 104, 106 can be coupled with the filter and blood can flowfrom the withdrawal line 104, through the filter 110, and into theinfusion line 106.

The blood filtration system can include a blood pump 112, and the bloodpump 112 can be configured to pump (e.g., convey, drive, push, or thelike) blood through the blood filtration system 100. In an example, theblood pump 112 can be a peristaltic pump, and the blood pump 112 canengage with the withdrawal line 104 to pump blood through the withdrawalline 104 and into the filter 110. The controller 102 can be configuredto operate the blood pump 112 to vary a speed of the blood pump 112 andaccordingly vary the flow rate of blood through the blood filtrationsystem 100 (e.g., the withdrawal line 104, the filter 110, the infusionline 106, or the like).

Referring again to FIG. 1, the blood filtration system 100 can include afiltration line 114 and a filtration pump 116. The filtration line 114can be configured to couple with the filter 110 (e.g., with a fitting),for instance the filtration line 114 can couple with a filtrate fluidport 111C. The filter 110 can be configured to transmit the filtratefluid (including one or more plasma constituents) to extracted by thefilter 110 to the filtrate fluid port 111C.

The filtration pump 116 can pump extracted filtrate fluid from thefilter 110, and into a filtrate fluid reservoir 118 (e.g., a bag,container, bladder, or the like). In some examples, the filtration pump116 can be a peristaltic pump that engages with the filtration line 114to pump the filtrate fluid through the filtrate fluid line 114. Thecontroller 102 can be configured to vary a speed of the filtration pump116 and accordingly vary the flow rate of filtrate fluid through theblood filtrate system 100 (e.g., the filtration line 114).

In some examples, the blood filtration system 100 can include one ormore access ports 120, for instance a first access port 120A, a secondaccess port 120B, and a third access port 120C. The access ports 120 canfacilitate the extraction of blood from the blood filtration system 100,or injection of substances (e.g., a blood thinner, for instance heparinor the like) into the blood within the blood filtration system 100. Inan example, the access ports 120A, 120B can be in communication with thewithdrawal line 104, and the access port 120C can be in communicationwith the infusion line 106.

A valve 122 (e.g., a mechanical check valve, or electronicallycontrolled valve) can be positioned between the access ports 120A, 120B,and the valves 122 can be configured to allow blood to flowunidirectionally within the withdrawal line 104 (e.g., flowing from thecatheter 108 to the filter 110). In this example, a substance can beinjected into the withdrawal line 104 at the access port 120B, and bloodcan be withdrawn from the access port 120A. Because the valve 122facilitates unidirectional flow within the withdrawal line 104, theblood including the substance will not be withdrawn from the access port120A, for instance because the access port 120A is upstream of theaccess port 120B). In an example, heparin can be infused into the accessport 120B and blood is drawn from the access port 120A to measure bloodclotting time parameters of a patient. Because the blood is drawn fromthe access port 120A, the withdrawn blood does not include heparin, andthe blood clotting time parameter determination is not affected by theheparin injection at the access port 120B. Accordingly, the performanceof blood filtration system 100 is thereby improved.

As shown in FIG. 1, the blood filtration system 100 can include one ormore sensors 124 (e.g., transducer, accelerometer, or the like), forinstance a first sensor 124A, a sensor 124B, and a sensor 124C. Thefirst sensor 124A can determine (e.g., measure, calculate, obtain,provide, or the like) the pressure within the withdrawal line 104, thesecond sensor 124B can determine the pressure within the infusion line106, and the third sensor 124C can determine the pressure within thefiltration line 114. The sensors 124 can include a fourth sensor 124D(e.g., a position sensor, or the like) and a fifth sensor 124E (e.g.,blood flow rate, or the like), and the sensor 124E can determine theblood flow rate through the system 100 (e.g., a component of the bloodcircuit 140, for example the withdrawal line 104).

The controller 102 can determine a venous pressure of the patient (e.g.,a pressure of a vein that is in communication with the catheter 108). Asdescribed herein, the controller 102 can operate the blood pump 112 andcontrol the speed of the blood pump 112. In an example, the controller102 can vary the speed of the blood pump 112, and stop the blood pump112 so that there is no blood flow through the blood filtration system100. Accordingly, pressure in the lines 104, 106 can reach equilibriumwith the venous pressure of the patient. As described herein, thesensors 124A, 124B can determine the pressure in the lines 104, 106.Accordingly, when the blood pump 112 is stopped, the controller 102 andsensors 124A, 124B can determine the venous pressure of the patient.

In some examples, the controller 102 can provide a notification of thevenous pressure of the patient. In an example, the controller 102 cancooperate with a display (e.g., a screen, for instance an LCD display)to display the determined venous pressure of the patient (e.g.,providing the determined venous pressure on a display included in ahousing for the system 100).

In another example, the controller 102 can determine a pressuredifferential between the sensors 124A, 124B. The controller 102 cancompare the pressure differential to a pressure differential threshold.In this example, if the pressure differential exceeds the pressuredifferential threshold, the controller 102 can provide a notification.In an example, the withdrawal line 104, can become blocked (e.g.,compressed, twisted, or the like, for instance by a patient leaning onthe withdrawal line), and the pressure in the withdrawal line 104 can begreater than the pressure of the infusion line 106.

The pressure differential between the lines 104, 106 can exceed apressure differential threshold, and the controller 102 can provide anotification that the pressure differential threshold has been exceeded.For instance, the controller 102 can provide a signal to a display todisplay a message that the withdrawal line 104 is blocked. In anotherexample, the controller 102 can provide a signal to an audio device(e.g., a speaker, a buzzer, or the like) to generate an audio signalthat notifies a patient (or a healthcare provider) that the withdrawalline is blocked. Accordingly, the patient or a healthcare provider canremedy the blockage of the withdrawal line 104 and restore proper bloodflow in the blood filtration system 100.

As described herein, the blood filtration system (e.g., the system 100)can determine the venous pressure of a patient. For example, the sensors124A, 124B can determine the pressure in the lines 104, 106, and thecontroller 102 can be in communication with the sensors 124A, 124B todetermine the venous pressure of the patient. The blood filtrationsystem 100 can compensate for pressure head (e.g., static pressure head,static head, the pressure exerted by, or the like) in one or more of thelines 104, 106. For example, the controller 102 can compensate for thepressure head in the lines 104, 106 due to gravitational forces due to achange in elevation (e.g., height, distance, offset or the like) betweena catheter tip 130 of the catheter 108 and the one or more of thesensors 124A, 124B that determine the pressure in the lines 104, 106. Insome approaches, a ruler is used to determine the elevation differencebetween the catheter tip 130 and the sensors 124A, 124B.

In an example, the catheter tip 130 can have a different elevation thanthe sensors 124A, 124B. For instance, the catheter tip 130 can belocated in vasculature of a limb of a patient (e.g., in a vein in an armof the patient, or the like), for example to withdraw or infuse bloodinto the vasculature. The sensors 124A, 124B can include positionsensors that determine the elevation where the sensors 124A, 124B arelocated (e.g., the elevation where the sensors 124A, 124B determines thepressure in the lines 104, 106). The catheter tip 130 can have adifferent elevation (e.g., as determined by the sensor 123D) than thesensors 124A, 124B. In an example, the patient can be located on a bedand blood filtration system 100 (including the sensors 124A, 124B) canbe located at a different elevation (e.g., on a cart, side table, or thelike). Accordingly, the system 100 can determine the difference inelevation between the catheter tip 130 and the elevation where thesensors 124A, 124B are located, for example to compensate for pressurehead in the lines 104, 106.

The difference in elevation between the sensors 124A, 124B and thecatheter tip 130 can affect the pressure determination by the sensors124A, 124B in the lines 104, 106, for instance due to pressure head inthe lines 104, 106. The system 100 can compensate for pressure head inthe lines 104, 106 when determining the venous pressure of the patient.For example, the system 100 can include a fourth sensor 124D, forexample an accelerometer. The sensor 124D can determine one or more ofposition, velocity, acceleration, jerk, or the like. The sensor 124D canbe coupled to the catheter 108, and the sensor 124D can be remote fromthe catheter tip 130. The sensor 124D can be communication with thecontroller 102, and the controller can determine an elevation differencebetween the catheter tip 130 and other components of the system 100(e.g., the sensors 124A, 124B) using the sensor 124D. For example, thesystem 100 can include one or more accelerometers that provide theelevation of components of the system 100 (e.g., the sensors 124A,124B), and the system 100 can determine elevation difference betweencomponents of the system 100 based on differences in gravitationalforces measured by the accelerometers.

The controller 102 can compensate for the pressure head in the lines104, 106 by determining the pressure head in the lines 104, 106 andusing the determined head pressure when determining the venous pressureof the patient (e.g., at the catheter tip 130). For example, thecatheter tip 130 can be elevated with respect to the sensors 124A, 124B.The sensors 124A, 124B can determine the pressure in the lines 104, 106,and the pressure in the lines 104, 106 can correspond (at leastpartially) with the venous pressure in the vasculature where thecatheter tip 130 is located. The pressure head in the lines 104, 106 dueto the difference in elevation between the tip and the sensors 124A,124B can affect the pressure determination of the sensors 124A, 124B.For instance, when the catheter tip 130 is located at a higher elevationthan the sensors 124A, 124B, the pressure head in the lines 104, 106 cancause the sensors 124A, 124B to determine a pressure that is higher thanthe actual venous pressure at the catheter tip 130 (e.g., because thepressure head increases the pressure above the actual venous pressuredue to the elevation difference between components of the system 100).Accordingly, the system 100 can determine the pressure head in the lines104, 106, and the system 100 can compensate for the pressure head in thelines 104, 106 when determining the venous pressure of the patient(e.g., at the catheter tip 130).

The blood filtration system 100 can determine density of blood in thevasculature of the patient, for example to improve the accuracy of thepressure head determination. For example, the pressure head in the lines104, 106 can be determined using the density of blood multiplied by thestandard gravity (e.g., 9.8 meters per second-squared) and multiplied bythe elevation difference between the sensors 124A, 124B. Accordingly,the density of blood can affect the determination of the pressure headin the lines 104, 106 by the controller 102.

The controller 102 can determine the density of blood in the vasculatureof the patient, for example to improve the pressure head determinationfor the lines 104, 106. In an example, the density of the blood can bedetermined using a hematocrit value of the blood of the patient (e.g.,as determined by the hematocrit sensor 126). Accordingly, the pressurehead determination by the controller 102 can be improved using densityof the blood.

The system 100 can include a blood circuit 140, and the blood circuit140 can include one or more components of the system 100. For example,the blood circuit 140 can include (but is not limited to) the withdrawalline 104, the infusion line 106, the catheter 108, the filter 110, thefiltration line 114, the filtrate fluid reservoir 118. The blood circuit140 can include components of the system that are in communication witha biological fluid of the patient.

The system 100 can include an activation key 150, and the activation key150 can be in communication with the controller 102, for example toprovide information about the blood circuit 140 to the controller 102.The activation key 150 can include (but is not limited to) an electronicdevice (e.g., a radio frequency identification tag, memory card, or thelike) that interconnects with the system 100 (e.g., wirelessly, or withwires, interconnects, or the like). For example, the activation key 150can include a radio frequency identification tag, and the system 100 cancommunicate with the activation key when the blood circuit 140 islocated proximate to the system 100. The activation key 150 can storeinformation provided by the system 100, for example usage informationrelated to the blood circuit 140.

In an example, the activation key 150 can be coupled with a portion ofthe blood circuit 140 (e.g., the activation key 150 can be coupled withthe filter 110). The activation key 150 can be unique to (e.g., pairedwith, tied to, associated with, or the like) an individual one of theblood circuit 140 to provide information to the system 100 about theindividual one of the blood circuit 140. For example, the activation key150 can provide the controller 102 with circuit characteristics of theblood circuit 140. The circuit characteristics can include (but are notlimited to) dimensions (e.g., size, length, diameter, or the like) ofthe lines 104, 106; dimensions of the filter 110; types of filters(e.g., a first filter intended for use with a child or a second filterintended for use with an adult, or the like); dimensions of the catheter108; or the like.

In some examples, the controller 102 can evaluate the circuitcharacteristics provided by the activation key 150 to operate the system100 at a configuration specific to the circuit characteristics of theblood circuit 140 coupled to the system 100. In an example, a firstblood circuit 140 can include a first filter 110 (e.g., a small filter)and a first activation key 150 that includes a first set of circuitcharacteristics (e.g., that correspond to a small filter). A secondblood circuit 140 can include a second filter 110, and the second filter110 (e.g., a large filter) can include a second set of circuitcharacteristics (e.g., that correspond to a large filter). The system100 can determine whether the first blood circuit 140 or the secondblood circuit 140 are coupled with the system 100, for example byevaluating the circuit characteristics stored by the activation key 150.The controller 102 can operate the system 100 according to the first setof circuit characteristics, for example by operating the blood pump 112at a first blood flow rate. The controller 102 can operate the system100 according to the second set of circuit characteristics, for instanceby operating the blood pump 112 at a second blood flow rate. Operatingthe system 100 in correspondence with the circuit parameters provided bythe activation key 150 can improve patient safety, for example bylimiting the rate that blood is withdrawn from a patient (e.g., wherethe blood circuit 140 is used with a pediatric patient that requires areduced blood flow rate in comparison to the blood flow rate for anadult patient).

As described herein, the activation key 150 can be in communication withthe controller 102. The controller 102 can provide the activation key150 with an activated characteristic, for example when the blood circuit140 is connected with other components of the system 100 (e.g., theblood pump 112). The activated characteristic can indicate whether theblood circuit 140 has been previously used with the system 100.Providing the activated characteristic to the activation key 150 caninhibit the reuse of the blood circuit 140, for example to inhibit(e.g., stop, prevent, block, or the like) the use of the blood circuit140 (or individual components of the blood circuit 140) with more thanone patient. In another example, the system 100 can limit the timeduration that an individual one of the blood circuit 140 can be usedwith the system 100 (e.g., to limit the time that the filter 110 can beused in renal replacement therapy).

The activation key 150 can store the activated characteristic when theactivated characteristic is provided by the controller 102. For example,the activation key 150 can include memory, and the activation key 150can store data corresponding to the activated characteristic in thememory (e.g., a solid state memory device, or the like). The system 100can read the activated characteristic stored by the activation key 150,for example to determine whether the blood circuit 140 was previouslycoupled with the system 100 (e.g., to inhibit more than one use of theblood circuit 140).

When the system 100 (e.g., the controller 102) determines whether theblood circuit 140 was previously coupled with the system 100, the system100 can inhibit operation of the system 100 (e.g., by inhibiting one ormore functions of the system 100. For example, the controller 102 caninhibit operation of the blood pump 112 to inhibit the system 100 fromwithdrawing blood from the patient. In another example, the system 100can provide a notification (e.g., by displaying a message on a display,for example an LCD screen, or the like) that the blood circuit 140 withan activated characteristic has been coupled with the system 100.

As described herein, the system 100 can limit the time duration that anindividual one of the blood circuit 140 can be used with the system 100.For example, the system 100 can limit a usage time that the bloodcircuit 140 is used with the system 100. In an example, the controller102 can provide the activation key 150 with an expirationcharacteristic. The controller 102 can provide the expirationcharacteristic after a specified time period (e.g., 12 hours, 2 days, 3days, or the like) from when the controller 102 provided the activatedcharacteristic to the activation key 150. The activation key 150 canstore one or more usage characteristics of the blood circuit 140. Forexample, the activation key 150 can store the usage time that the bloodcircuit 140 has been used during therapy with the system 100. In someexamples, the system 100 can provide a notification (e.g., bytransmitting a message to a mobile device, or the like) that the usagetime of the blood circuit 140 is approaching the specified time periodwhere the system 100 will inhibit the use of the blood circuit 140 withthe system 100 (e.g., by providing the expiration characteristic to theactivation key 150). The notification can notify a health provider tochange (e.g., swap, or the like) the used blood circuit 140 with a newblood circuit 140 (e.g., when the usage time reaches 80 percent of thespecified time period).

FIG. 1 shows the blood filtration system 100 can include a hematocritsensor 126. In some examples, the hematocrit sensor 126 can include anoptical hematocrit sensor, and the hematocrit sensor 126 can be coupledwith one or more of the lines 104, 106, and the hematocrit sensor 126can determine a hematocrit value (e.g., level, or the like) of thepatient. In an example, the hematocrit sensor 126 can be located betweenthe catheter 108 and the valve 122, for instance to monitor thehematocrit value of the patient prior to injection of a fluid (e.g.,heparin or saline) into the blood (e.g., at the access port 120B).Accordingly, the hematocrit value determination can be improved with thesystem 100.

In an example, the controller 102 can be configured to control the speedof the blood pump 112 and set the flow rate of blood through the filter110 at a first blood flow rate. Additionally, the controller 102 can beconfigured to control the speed of the blood pump 112 and set the flowrate of blood through the filter at a second blood flow rate. The firstblood flow rate can be different than the second blood flow rate. Thecontroller 102 can determine the hematocrit at the second blood flowrate. The controller 102 can control the speed of the blood pump 112 andset the flow rate of blood at the first blood flow rate afterdetermining the hematocrit value, for example after determining thehematocrit value at the second blood flow rate.

The controller 102 can control the speed of the blood pump 112 tomeasure the hematocrit value because the hematocrit value can varyaccording to the speed of the blood pump 112, and controlling the speedof the blood pump can improve the accuracy of the hematocrit valuedetermination. For instance, the hematocrit value determination by thehematocrit sensor 126 can be affected by the flow rate of blood throughthe filter. In this example, the speed of the blood pump 112 can vary,and the determined hematocrit value of the patient can vary according tothe speed of the blood pump 112. Accordingly, measuring the hematocritvalue with the blood pump 112 at a consistent speed can improve theaccuracy of the hematocrit value determination. Accordingly, varying thespeed of the blood pump 112 can account for a source of error indetermining the hematocrit value and the performance of the bloodfiltration system 100 is thereby improved.

As described herein, the blood filtration system 100 can determine ahematocrit value of a patient. The hematocrit value of the patient canbe defined by Equation (1). H=RBCV/BV, where H is the hematocrit value,RBCV is the red blood cell volume, and BV is the total blood volume(e.g., the RBCV plus plasma volume). Equation (1) can be rearranged todetermine the red blood cell volume, as shown in Equation (2):BV=RBCV/H. The derivative of Equation (2) is shown in Equation (3):

$\frac{d({BV})}{dt} = {{RBCV}*\frac{d( \frac{1}{H} )}{dt}}$

where 1/H is an inverse of the hematocrit value. The change of bloodvolume for a patient undergoing blood filtration with the bloodfiltration system 200 is shown in Equation (4):

$\frac{d({BV})}{dt} = {{PRR} - {FR}}$

where PRR is the plasma refill rate, and FR is the filtration rate(e.g., the rate of filtrate fluid flowing from the filter 110). Theplasma refill rate is the rate that the plasma volume changes withrespect to time, from within the body of the patient (e.g., the flowingof plasma water into the blood stream from interstitial spaces of thebody into the venous system of the patient).

The filtration rate can be varied (e.g., changed), for instance byvarying the speed of the filtration pump 116, and the change infiltration rate is shown in Equation (5):

ΔFR=FR ₂ −FR ₁

Combining Equations (3) and (4) yields Equation (6):

${{PRR} - {FR}} = {{RBCV}*\frac{d( \frac{1}{H} )}{dt}}$

As described herein the filtration rate (FR) can be varied, andaccordingly substituting Equation (6) into Equation (5), and performingadditional algebra yields Equation (7):

${RBCV} = \frac{\Delta\;{FR}}{\frac{d( \frac{1}{H\; 2} )}{dt} - \frac{d( \frac{1}{H\; 1} )}{dt}}$

where H₁ is the hematocrit value at the first filtration rate (FR₁), andH₂ is the hematocrit value at the second filtration rate (FR₂). Thecontroller 102 can be configured to determine a red blood cell volumeusing Equation (7).

Substituting Equation (7) into Equation (1) yields Equation (8):

${{BV}( {{{at}\mspace{14mu} t} = {tx}} )} = \frac{RBCV}{H_{t = {tx}}}$

Performing algebraic manipulation of Equation (8) yields Equation (9):

${{PV}( {{{at}\mspace{14mu} t} = {tx}} )} = {{RBCV} \times ( {( \frac{1}{Hx} ) - 1} )}$

where PV is the plasma volume of the patient.

The controller 102 can use Equation (9) to determine the plasma volumeof the patient, and determine when to stop filtering the blood of thepatient. In another example, the red blood cell volume can be determinedusing Equation (10):

${RBCV} = {({FV})*\frac{{Hfinal}*{Hinit}}{{Hfinal} - {Hinit}}}$

where FV is the volume of filtrate fluid extracted from the patient(e.g., by the filtration pump 16), H_(init) is the hematocrit value atthe beginning of filtration therapy (e.g., when the filtration pump 116is started), and H_(final) is the hematocrit value at the end offiltration therapy (e.g., when the filtration pump 116 is stopped).H_(init) and H_(final) can be determined using the hematocrit sensor 126

Determining the red blood cell volume with the blood filtration system100 can reduce the need to determine the red blood cell volume withother methodologies. For instance, a tracer (e.g., a radioactive tracer,cardiac green, or saline, or the like) can be injected into a bloodstream of the patient. One or more blood samples can be withdrawn fromthe patient to determine the red blood cell volume. The red blood cellvolume can be used to determine the quantity of the one or more plasmaconstituents to extract from the patient. In this example, the red bloodcell can be inputted into the blood filtration system, for instance atthe beginning of therapy. In another example, the controller 102 candetermine the red blood cell volume according to Equation (7) orEquation (10). In some examples, the controller 102 is optionallyconfigured to set an extraction rate of filtrate fluid from the filter110 using the determined red blood cell volume or the determinedhematocrit value of the patient.

As described herein, the plasma refill rate is the rate that the plasmavolume changes with respect to time, from within the body of the patient(e.g., the flowing of plasma water into the blood stream frominterstitial spaces of the body). The plasma refill rate can affect theplasma volume determination, for instance when using Equation (9). Theplasma refill rate can be determined using Equation (11):

${PRR} = \frac{{FV}*\lbrack {{H\; 1*H\; 2} - {H\; 1*H\; 3}} \rbrack}{{{\tau 1}*\lbrack {{H\; 1*H\; 2} - {H\; 1*H\; 3}} \rbrack} - {{\tau 2}*\lbrack {{H\; 1*H\; 3} - {H\; 2*H\; 3}} \rbrack}}$

where FV is the volume of filtrate fluid extracted from the patient(e.g., by the filtration pump 116), H1 is a first hematocrit valuedetermination, H2 is a second hematocrit value determination, H3 is asecond hematocrit value determination, τ1 is the time difference betweenthe H1 and H2 determinations, and τ2 is the time difference between theH2 and H3 determinations. H1 can be determined at the beginning offiltration therapy (e.g., when the filtration pump 116 is started). H2can be determined at the end of filtration therapy (e.g., when thefiltration pump 116 is stopped). H3 can be determined after a waitingperiod (e.g., one hour) where the blood pump is operated (e.g., turnedon), while the filtration pump 116 is not operated (e.g., turned off).Accordingly, the blood filtration system 100 can determine the plasmarefill rate and use the plasma refill rate to determine when to stoptherapy of the patient, and when the patient has reached euvolemia. Thecontroller 102 can use one or more of Equations (1)-(11) during therapyto determine a quantity of filtrate fluid to extract from the patient,and determine how much plasma remains in the patient at a given point intime. Accordingly, the controller 102 using one or more of Equations(1)-(11) (or Equations (1)-(17) can improve the performance of the bloodfiltration system (e.g., the system 100).

As described herein, Equation (1) is H=RBCV/BV, where H is thehematocrit value, RBCV is the red blood cell volume, and BV is the totalblood volume. Equation (1) can be equivalent to: H=RBCV/(RBCV+PV), wherePV is the plasma volume. Equation (12) facilitates the determination ofthe density of the blood of the patient (e.g., whole blood, unfilteredblood, or the like):

$\rho_{b} = {\frac{mass}{volume} = \frac{{\rho_{r}*{RBCV}} + {\rho_{p}*{PV}}}{{RBCV} + {PV}}}$

where ρ_(b) is the density of the blood of the patient, ρ_(r) is thedensity of a single blood cell, ρ_(p) is the density of plasma, PV isthe plasma volume. In an example, the system 100 can determine one ormore of the hematocrit value, the density of plasma ρ_(p), and thedensity of a single blood cell ρ_(r). For example, the system candetermine the hematocrit value H, the density of plasma ρ_(p), or thedensity of a single blood cell ρ_(r) using one or more equations orconstants, including (but not limited to) Equations (1)-(17). Performingone or more mathematical operations on Equation (1) yields Equation(13):

(H−1)*RBCV+H*PV=0

Performing one or more mathematical operations on Equation (12) yieldsEquation (14):

(ρ_(b)−ρ_(r))*RBCV+(ρ_(b)−ρ_(p))*PV=0

Performing one or more mathematical operations on Equations (13) and(14), for example by simultaneously solving Equations (13) and (14)yields Equation (15):

$H = \frac{\rho_{b} - \rho_{p}}{\rho_{r} - \rho_{p}}$

The density of blood of the patient ρ_(b) can be determined usingEquation (15), for example by performing one or more mathematicaloperations on Equation (15) to yield Equation (16):

ρ_(b)=ρ_(p)(1−H)+H*ρ _(r)

Accordingly, the system 100 can determine the density of blood of thepatient ρ_(b), using the hematocrit value H determination.

FIG. 1 shows the withdrawal line 104 in communication with the sensor124A and the infusion line in communication with the sensor 124B. Asdescribed herein, the sensors 124A can determine pressure in thewithdrawal line 104, and the sensor 124B can measure pressure in theinfusion line 106. The sensors 124A, 124B can be in communication withthe controller 102, and the controller 102 can determine the pressure inthe lines 104, 106 using the sensors 124A, 124B.

When the controller 102 operates the blood pump 112, the blood pump 112generates a negative pressure in withdrawal line 104 to withdraw bloodfrom the vasculature where the catheter tip 130 is located. The bloodpump 112 can generate a positive pressure in the infusion line 106 toinfuse blood into the vasculature where the catheter tip 130 is located.The magnitude of the pressure in lines 104, 106 can increase tocorrespondingly increase the blood flow rate within the lines 104, 106.

The blood circuit 140 (including the lines 104, 106) can have a totalresistance characteristic that corresponds to an amount of resistance inthe blood circuit 140 to the flow of blood through one or morecomponents of the blood circuit, for instance the lines 104, 106 or thefilter 110. One or more characteristics can contribute to the totalresistance characteristic of the lines 104, 106. For example, theresistance characteristic of the lines 104, 106 can increase due toocclusion (e.g., clotting, obstruction, or the like) of the bloodcircuit 140 (e.g., in or around the catheter 108), changes to thevasculature (e.g., inflammation of walls of the vasculature, compressionof the vasculature, or the like), hemoconcentration of the blood, or thelike. The resistance characteristic (e.g., transverse or longitudinal)of the filter 110 can contribute to the total resistance characteristicof the blood circuit 140.

An increase in the resistance characteristic of the lines 104, 106 (orother components of the blood circuit 140) can diminish blood flowthrough the lines 104, 106. The diminished blood flow due to theincrease in the resistance characteristic of the lines 104, 106 canreduce the performance of the system 100, for example by reducing themaximum blood flow rate through the blood circuit 140 or the rate thatthe one or more blood constituents can be removed from the blood by thefilter 110. The resistance characteristic of the lines 104, 106 canincrease to the point where the blood pump 112 is unable to maintainflow within the lines 104, 106 (e.g., because the forces resisting flowin the lines exceeds the forces generated by the blood pump 112).Accordingly, an increase in the resistance characteristic of the lines104, 106 can diminish the performance of the blood filtration system100.

The system 100 can determine a total resistance characteristic for oneor more components of the blood circuit 140, for example the withdrawalline 104 and the infusion line 106. In an example, a withdrawal lineresistance characteristic can correspond to the resistance in thewithdrawal line 104 to the flow of blood through the withdrawal line104. The withdrawal line resistance characteristic can correspond to thepressure in the withdrawal line 104 divided by the actual blood flowrate of system 100 (e.g., as determined by sensor 124E). The actualblood flow rate of the system 100 can vary from a set point that thecontroller 102 operates the blood pump 112 at. For example, theresistance characteristic of the lines 104, 106 can reduce the actualblood flow rate through the blood circuit 140 because the resistance tothe flow of blood in the lines 104, 106 decreases the efficiency of theblood pump 112.

The infusion line resistance characteristic can correspond to theresistance in the infusion line 106 to the flow of blood through theinfusion line 106. The infusion line resistance characteristic cancorrespond to the pressure in the infusion line 106 divided by thedifference between the actual blood flow rate and the filtration rate ofthe system (e.g., as determined by controller 102 in communication withthe sensors 124). An increase in the magnitude of the resistancecharacteristic of the blood circuit 140 (including the lines 104, 106)can increase the force necessary to withdraw blood from (or infuse bloodinto) the patient by the blood pump 112. The increase in the magnitudeof the resistance characteristic of the blood circuit 140 can result in(or be an indication of) clotting in the blood circuit 140.

The hematocrit value of the patient can contribute to the totalresistance characteristic of the blood circuit 140. As described herein,the blood filtration system 100 can determine the hematocrit value ofthe patient. Hemoconcentration (e.g., an increase in the hematocrit) ofthe blood of the patient can increase the density or viscosity of theblood. Accordingly, an increase in hematocrit of the patient canincrease the resistance of blood to flow in the blood circuit 140. Thesystem 100 can determine a hemoconcentration resistance characteristicusing the determined hematocrit value of the patient (or a determinedvenous pressure of the patient). The hemoconcentration resistancecharacteristic can correspond to the resistance to the flow of the bloodof the patient through the blood circuit 140.

In an example, the total resistance characteristic of the lines 104, 106can increase due to occlusion (e.g., clotting, obstruction, or the like)of the blood circuit 140, changes to the vasculature, hemoconcentrationof the blood, or the like. The system 100 can determine an occlusionresistance characteristic of the lines 104, 106. The occlusionresistance characteristic can correspond to the resistance of the flowof blood through the lines 104, 106 due to an occlusion of the circuitor changes in vasculature of the patient. The occlusion resistancecharacteristic can correspond to the difference between the withdrawalline resistance characteristic and the hemoconcentration resistancecharacteristic. The occlusion resistance characteristic can correspondto the difference (e.g., by performing a subtraction mathematicaloperation) between the infusion line resistance characteristic and thehemoconcentration resistance characteristic. Accordingly, the system 100can determine what resistance characteristics (e.g., thehemoconcentration resistance characteristic, or the like) arecontributing to the total resistance characteristic for the bloodcircuit 140 (including the lines 104, 106).

The system 100 can provide a notification of one or more of theresistance characteristics that are determined by the system 100. Forexample, the system 100 can provide a notification on a display of thewithdrawal line resistance characteristic or the infusion lineresistance characteristic. In another example, the system 100 canprovide a notification of the occlusion resistance characteristic toinform a user (e.g., a healthcare provider, or the like) that resistancein the blood circuit 140 is due to an occlusion or the changes invasculature of the patient. For example, the notification of theocclusion resistance characteristic can allow a user to applyappropriate corrective measures to increase the lifetime of the bloodcircuit 140. In an example, the user can inject an anticoagulant to tryand reduce clotting in the blood circuit 140. In another example, theuser can manipulate the catheter 108 to reposition the catheter tip 130relative to the vasculature of the patient (e.g., to move the cathetertip 130 away from a wall of the vasculature).

In some examples, the system 100 provides a notification of pressures inthe blood circuit 140 (e.g., pressure in the withdrawal line 104). Thepressure in the withdrawal line 104 can be indicative of the totalresistance characteristic of the blood circuit. However, as describedherein, the total resistance characteristic depends upon othercharacteristics (e.g., variables, or the like), including (but notlimited to) the occlusion resistance characteristic and thehemoconcentration resistance characteristic. Determining the occlusionresistance characteristic and the hemoconcentration resistancecharacteristic can facilitate diagnosis for the cause of an increase inthe total resistance characteristic of the blood circuit 140. Diagnosingthe cause of the increase in the total resistance characteristic of theblood circuit 140 can facilitate appropriate corrective measures toreduce the total resistance characteristic of the blood circuit 140.Accordingly, the system 100 can improve the lifetime of the bloodcircuit 140, for example by reducing replacement of components of theblood circuit 140 (e.g., the filter 112) due to clotting.

FIG. 2 shows a schematic view of an example of a second blood filtrationsystem 200. The blood filtration system 200 can include, but is notlimited to, the blood pump 112, the filter 110, the filtration line 114,and the filtration pump 116. Additionally, the filtration system 200 caninclude a harvest fluid line 210, and can include a harvesting pump 220.The harvest fluid line 210 can be in communication with the filtratefluid port 111C, for example, the harvest fluid line 210 can be coupledto the filtration line 114, and the harvest fluid line 210 can receivefiltrate fluid from the filtration line 114.

In some examples, the filter 110 includes a harvesting port 111D. Theharvesting port 111D can be configured to receive filtrate fluid. In anexample, the harvest fluid line 210 is coupled with the harvesting port111D, and the harvesting port 111D is in communication with the filtratefluid port 111C through the harvest fluid line 210. The harvesting pump220 can engage with the harvest fluid line 210 and pump filtrate fluidfrom the filtrate fluid port 111C to the harvesting port 111D. Thecontroller 102 can operate (e.g., activate, turn on, energize, provide acontrol signal to, or the like) the harvesting pump 220 to extractfiltrate fluid from a filtrate reservoir (e.g., the filtrate fluid port111C, the filtration line 114, or the filtrate fluid reservoir 118) andinject the filtrate fluid into the harvesting port 111D to dilute theblood flowing through the filter.

In some examples, the harvesting port 111D is included in (e.g., extendsfrom, or is in communication with) a filter body 230 of the filter 110.In another example, the harvesting port 111D is coupled with the bloodinlet port 111A. Optionally, a one-way valve is included between thefiltrate fluid port 111C and the harvesting port 111D, for instance toinhibit blood flow within the harvest fluid line 210 while allowingfiltrate fluid to flow from the filtrate fluid port 111C to theharvesting port 111D. As described in greater detail herein, theharvesting port 111D can provide filtrate fluid into the filter todilute blood within the filter and inhibit clotting of blood flowingthrough the filter.

FIG. 3 shows a flowchart of a first method 300 for preserving a filterfor a blood filtration system (e.g., the blood filtration system 100 orthe blood filtration system 200). In describing the method 300,reference is made to one or more components, features, functions andoperations previously described herein. Where convenient, reference ismade to the components, features, operations and the like with referencenumerals. The reference numerals provided are exemplary and are notexclusive. For instance, components, features, functions, operations andthe like described in the method 300 include, but are not limited to,the corresponding numbered elements provided herein and othercorresponding elements described herein (both numbered and unnumbered)as well as their equivalents. Additionally, the method 300 can beincluded in instructions on a computer readable medium, and theinstructions can be carried out by the controller 102 (e.g., processingcircuitry).

At operation 310 the blood flow rate can be periodically set to areference level (e.g., operating the blood pump 112 at the second bloodflow rate). At operation 320 the hematocrit value of the patient can bedetermined (e.g., with the hematocrit sensor 126 shown in FIG. 1). Afilter resistance of the filter 110 can be determined at operation 330.In an example, the filter resistance can be determined by determining apressure differential between the sensors 124A, 124B (shown in FIG. 1).The filter resistance can be determined with the blood pump operating,for instance at the second blood flow rate. At operation 340, afiltration fraction can be determined according to Equation (17):

${{Filtration}\mspace{14mu}{Fraction}} = \frac{{Filtration}\mspace{14mu}{Flow}\mspace{14mu}{Rate}}{( {1 - {{Hematocrit}\mspace{14mu}{Value}}} )( {{Blood}\mspace{14mu}{Flow}\mspace{14mu}{Rate}} )}$

At operation 350, the hematocrit value is compared to a hematocritthreshold (e.g., 0.50) and if the hematocrit value is greater than thehematocrit threshold, or if the filtration fraction is greater than afiltration fraction threshold (e.g., 0.20), the filtration fraction canbe reduced at operation 360. Reducing the filtration fraction can bereduced, for instance, by the controller 102. The controller 102 can beconfigured to control a speed of one or more pumps to adjust thefiltration fraction of the system. The controller can vary the speed ofthe one or more pumps (e.g., the filtration pump 116, the blood pump112, or the like) to adjust the filtration fraction

Controlling the filtration fraction can be used to control the rate ofremoving plasma constituents while maintaining preferred patientdiagnostic parameters.

Additionally, controlling the filtration fraction can be used to reduceclogging of the extracorporeal components of a blood filtration system(e.g., the blood filtration system 100, or the blood filtration system200). In this example, if the hematocrit value is less than thehematocrit threshold, or if the filtration fraction is less than afiltration fraction threshold (e.g., 0.20), the blood flow rate of thesystem can be set to a user set blood flow rate (e.g., operating theblood pump 112 at the first blood flow rate).

FIGS. 4A-4H show a schematic view of an example of a third bloodfiltration system 400. As shown in FIG. 4A, the filtration system 400can include the controller 102, the withdrawal line 104, the infusionline 106, the catheter 108, the filter 110, the blood pump 112, thefiltration line 114, the filtration pump 116, the filtration fluidreservoir 118, and the one or more valves 122. The valves 122 caninclude a check valve, pinch valve (e.g., a valve that pinches a portionof the blood circuit 140, for instance the lines 104, 106),electromechanical valve, or the like. The catheter 108 can be insertedinto vasculature 410 of a patient (e.g., a central venous system,peripheral venous system, basilic vein, cephalic vein, brachial vein,the axillary vein, the subclavian vein, the brachiocephalic vein, or thelike). The blood pump 112 can be in communication with a blood reservoir430. In an example, the withdrawal line 104 can be in communication witha blood reservoir line 420. The controller 102 can be configured tocontrol the blood pump 112 to operate the blood pump 112 in a first flowdirection to transmit blood from the patient into the blood reservoir.

Additionally, the controller 102 can be configured to control the bloodpump 112 to transmit blood from the blood reservoir 430 to the filter110. For instance, the blood pump 112 can be controlled to operate theblood pump 112 in a second flow direction. The second flow direction canbe opposite to the first flow direction. As described herein, the bloodfiltration system 400 can include the one or more check valves 122, forinstance a first valve 122A, a second valve 122B, a third valve 122C,and a fourth valve 122B. The first valve 122A can allow forunidirectional flow within the withdrawal line 104 and prevent bloodfrom being transmitted into the catheter 108 when the blood pump 112 isoperated in the second flow direction. Accordingly, the valve 122Afacilitates transmission of blood from the blood reservoir 430 to thefilter 110.

In some examples, the valves 122 are operated out of phase with eachother. For instance, the controller 122A can operate the valve 122A topermit flow through the withdrawal line 104. The controller 102 canoperate the valve 122D to inhibit flow through the infusion line 106.Accordingly, the controller 102 can operate the valve 122A out of phasewith the valve 122D. Inhibiting the flow in one or more of the lines104, 106 can facilitate unidirectional flow through the system 100(e.g., the blood circuit 140). In an example, operating the valves 122(e.g., the valves 122A, 122D, or the like) out of phase can inhibit theflow of blood from the infusion line 106 to the withdrawal line (or fromthe withdrawal line 104 to the infusion line 106). For instance, closingthe valve 122D can facilitate withdrawal of blood from the vasculature410 of the patient while inhibiting flow of blood from the infusion line106 to the withdrawal line 104. The valve 122A can be operated tofacilitate unidirectional flow in the system 400, for example by closingthe valve 122A to inhibit flow from the withdrawal line 104 to theinfusion line 106 (or from the withdrawal line 104 to the vasculature410 during infusion of the blood into the vasculature 410. Accordingly,operating the valves 122 out of phase with each other can facilitateunidirectional flow through the system 400 (or other systems describedherein, for example the system 100, or the like).

The filtration pump 116 can pump extracted filtrate fluid from thefilter 110, and into the filtrate fluid reservoir 118. In some examples,the filtration pump 116 can be a peristaltic pump that engages with thefiltration line 114 to pump the filtrate fluid through the filtratefluid line 114. The controller 102 can be configured to vary a speed ofthe filtration pump 116 and accordingly vary the flow rate of filtratefluid through the blood filtrate system 100 (e.g., the filtration line114).

The system 400 can facilitate the use of a single lumen catheter 108,however the present subject matter is not so limited. For instance, thecatheter 108 can include a single passage, and blood can be withdrawnand infused within the single passage. The single lumen catheterfacilitates increased blood flow in the system 400. Accordingly, theincreased blood flow reduces clogging in the filter 110, therebyimproving the performance of the system 400.

As shown in FIG. 4B, in some examples, the catheter 108 includes awithdrawal port 440A that can be isolated from an infusion port 440BFIG. 4C shows that the blood filtration system 400 can include adiverter valve 450. The diverter valve 450 can be controlled by thecontroller 102, for instance the controller 102 can provide a controlsignal to operate the diverter valve 450. The diverter valve 450 can beoperated to allow for blood to flow in one or more directions. In anexample, the diverter valve 450 can be operated to allow blood to flowfrom the catheter 108 to the blood reservoir 430, while preventing bloodfrom being withdrawn from other portions of the blood filtration system400 (e.g., the filter 110).

FIG. 4D shows another example of the blood filtration system 400. Insome examples, the blood filtration system 400 does not include the oneor more check valves 122. For instance, the blood pump 112 can withdrawblood from the catheter and transmit the blood into the blood reservoir430. The operating direction of the blood pump 112 can be changed (e.g.,operated in the second flow direction) to transmit blood back into thefilter 110. For instance, the blood in the system 400 can be transmittedthrough the filter 110 in a plurality of cycles. In another example, forinstance as shown in FIG. 4A, blood can be transmitted through thefilter 110 in a single cycle (e.g., in a continuous circuit). Thecontroller 102 can be configured to operate the filtration pump 116during a single cycle through the filter 110, or to operate thefiltration pump 116 during one or more of the plurality of cyclesthrough the filter 110.

As shown in FIG. 4E, the blood filtration system 400 can include asingle valve 122. Blood can be transmitted from the catheter 108,through the valve 122A, and into the blood reservoir 430. The operatingdirection of the blood pump 112 can be reversed, and blood can betransmitted through the filter 110 and into the catheter 108. In someexamples, and as shown in FIGS. 4F-4G, the blood pump 112 can pump a gas(e.g., air, nitrogen, or the like) to correspondingly pump blood intoand out of the blood reservoir 430. For instance, the blood pump 112 candecrease the gas pressure in the blood reservoir 430, andcorrespondingly draw blood into the blood reservoir from the catheter108. The operating direction of the blood pump 112 can be changed, andthe gas pressure inside the blood reservoir 430 can be increased. Inthis example, the increase in gas pressure can correspondingly cause theblood flow from the blood reservoir 430 and into the filter 110. In someexamples the blood filtration line 420 can be in communication with theatmosphere, for instance through an air filter 460. The communication ofthe blood filtration line 420 with the atmosphere can facilitate theblood pump 112 changing the pressure within the blood reservoir 430.

Further, and as described in greater detail herein, the blood filtrationsystem 400 can include one or more filters 110. For example, the bloodfiltration system 400 can include a first filter 110A and a secondfilter 110B. In this example, the filters 110A, 110B are incommunication with the filtration pump 116 (or a plurality of filtrationpumps 116), and the filtration pump 116 extracts filtrate fluid from thefilters 110A, 110B. In an example, the filter 110A filters filtratefluid from the blood of the patient when the blood pump 112 operates ina first direction (e.g., during withdrawal of blood from the patient).In another example, the filter 110B filters filtrate fluid from theblood of the patient when the blood pump operates in a second direction(e.g., during infusion of blood into the patient). The system 100 candetermine the amount of filtrate fluid removed from the blood of apatient. For example the system 100 can be in communication with a scalethat weights the reservoir 118. In another example, the sensors 124 caninclude a flow meter in communication with the line 114 and thecontroller 102 determines the amount of filtrate fluid removed from thepatient with the flow meter.

FIG. 5 shows a schematic view of a fourth blood filtration system 500.As described herein, the filter 110 can include a filter body 230, afilter inlet port 111A, a filter outlet port 111B, and a filtrate fluidport 111C. The filter inlet port 111A, filter outlet port 111B, andfiltrate fluid port 111C can be included in the filter body 230, and theports 111A, 111B, 111C facilitate coupling the filter 110 withadditional components of a blood filtration system (e.g., one or more ofthe blood filtration systems 100, 200, 400).

In an example, blood can flow into the filter body 230 through thefilter inlet port 111A, flow through the filter body 230, and out of thefilter outlet port 111B. In an example, blood can cycle through thefilter 110 multiple times, for instance as described with reference toFIG. 4G. The filter 110 can be configured to reduce the amount offiltrate fluid in the blood flowing through the filter 110, and transmitthe extracted filtrate fluid to the filtrate fluid port 111C.

As described herein, the filter 110 can include the harvesting port111D. In some examples, the harvesting port 111D can be coupled to thefilter inlet port 111A, and the harvesting port 111D can be incommunication with the filter inlet port 111A. Introducing filtratefluid into the harvesting port 111D can mix filtrate fluid with bloodentering the filter inlet port 111A, and accordingly dilute the bloodwith the filtrate fluid.

In some examples, the filter 110 can include one or more valves toinhibit the flow of fluid with respect to the filter 110. In an example,the filter can include a filter inlet valve 505, a filter outlet valve510, a filtration fluid valve 520, and/or a harvesting valve 530. Thevalves 505, 510 can be in communication with the ports 111A, 111B,respectively, and can stop (e.g., inhibit) the flow of blood withrespect to the filter 110 (e.g., preventing the transmission of bloodinto or out of the ports 111A, 111B). The valve 520 can be incommunication with the port 111C, and can stop the flow of filtratefluid with respect to the filter 110 (e.g., preventing the transmissionof blood into or out of the port 111C). The valve 530 can be incommunication with the port 111D, and can stop the flow of filtratefluid and/or blood with respect to the filter 110 (e.g., preventing thetransmission of filtrate fluid and/or blood into or out of the port111D).

Additionally, the withdrawal line 104 can be in communication with afirst line valve 540, the infusion line 106 can be in communication witha second line valve 550, the filtrate fluid line 114 can be incommunication with a third line valve 560, and the harvesting line 210can be in communication with a fourth line valve 570. The valves 540,550, 560, 570 can stop the flow with respect to the lines 104, 106, 114,210, respectively.

The valves 505, 510, 520, 530, 540, 550, 560, 570 can facilitateinterchanging the filter 110 with a different filter 110, for instanceif the filter 110 becomes clogged. For instance, the valves 505, 510,520, 530, 540, 550, 560, 570 can be closed, and coupling members 580(e.g., fittings) can be separated to detach the lines 104, 106, 114, 210from the filter. A replacement filter 110 can be located proximate tothe lines 104, 106, 114, 210, and the coupling members 180 can bereattached to the replacement filter 110. The valves 505, 510, 520, 530,540, 550, 560, 570 can be opened, and flow throughout the bloodfiltration system 500 is reestablished. Accordingly, the performance ofthe blood filtration system 500 is thereby improved. In some examples,the members 580 are integral with the valves 505, 510, 520, 530, 540,550, 560, 570.

In an example, the valves 540, 550, 560, 570 include a ball valve. Inanother example, the valves 540, 550, 560, 570 include one or more pinchvalves that compresses the lines 104, 106, 114, 210 to inhibit the flowof fluid through one or more of the lines 104, 106, 114, 210. In anexample, the controller 102 operates the pinch valves to inhibit flow offluid through the lines 104, 106, 114, and 210.

The blood filtration system 500 can include the controller 102, and thecontroller 102 can be configured to determine one or more filterresistances of the filter 110. In an example, the filter 110 can have alongitudinal resistance characteristic, and the longitudinal resistancecharacteristic can include the resistance of the flow of a fluid (e.g.,blood) through a length of the filter 110, for instance as denoted bythe arrow 595A. In one example, the controller 102 can determine thelongitudinal filter resistance characteristic by determining thepressure at an inlet pressure sensor 590A that is in communication withthe inlet port 111A of the filter 110.

As the filter 110 filters blood, the filter 110 can become clogged, forinstance due to clotting in the filter 110. As the filter 110 becomesclogged, the longitudinal filter resistance of the filter 110 increases,because the clogged filter increases the amount of force necessary topump blood through the filter 110. Accordingly, the pressure at theinlet pressure sensor 590A can increase.

The controller 102 can compare longitudinal filter resistancecharacteristic to a filter resistance threshold, for instance a firstfilter resistance threshold, and determine if the longitudinal filterresistance characteristic exceeds the first filter resistance threshold.In this example, when the longitudinal filter resistance exceeds (e.g.,is greater than) the first filter resistance threshold, the controller102 can operate (e.g., with a control signal) a harvesting pump (e.g.,the harvesting pump 220 shown in FIG. 1). Operating the harvesting pumpcan inject a fluid (e.g., filtrate fluid, saline, heparin, or the like)into the port 111D, and introduce the fluid into blood flowing into thefilter 110. For instance, injecting the filtrate fluid into the port111D can reduce the longitudinal filter resistance characteristic, forinstance by diluting blood clotted in the filter 110. The controller 102can be configured to operate the harvesting pump and stop injectingfiltrate fluid into the port 111D when the longitudinal filterresistance characteristic exceeds (e.g., is less than) a second filterresistance threshold. Accordingly, the performance of the bloodfiltration system 500 is improved because a lifetime of the filter 110can be extended by reducing clogging of the filter 110.

In another example, the filter 110 can have a transverse resistancecharacteristic, and the transverse resistance characteristic can includethe resistance of the flow of a fluid (e.g., filtrate fluid) through athickness of the filter 110, for instance as denoted by the arrow 595B.In one example, the controller 102 can determine the transverse filterresistance characteristic by determining the pressure at a filtrationpressure sensor 590C that is in communication with the filtrate fluidport 111C of the filter 110. As the filter 110 filters blood, the filter110 can become clogged, for instance due to clotting in the filter 110.As the filter 110 becomes clogged, the transverse filter resistance ofthe filter 110 increases, because the clogged filter increases theamount of force necessary to extract filtrate fluid from the filter 110(e.g., with the filtration pump 116 shown in FIG. 1). Accordingly, thepressure at the inlet pressure sensor 590A can increase.

The controller 102 can compare the transverse resistance characteristicto a filter resistance threshold, for instance a first filter resistancethreshold, and determine if the transverse resistance characteristicexceeds (e.g., is greater than) the first filter resistance threshold.In this example, when the transverse filter resistance exceeds the firstfilter resistance threshold, the controller 102 can operate (e.g., witha control signal) a harvesting pump (e.g., the harvesting pump 220 shownin FIG. 1). Operating the harvesting pump can inject filtrate fluid intothe port 111D, and dilute the blood flowing into the filter 110.Injecting the filtrate fluid into the port 111D can reduce thetransverse filter resistance characteristic, for instance by dilutingblood clotted in the filter 110. The controller 102 can be configured tooperate the harvesting pump and stop injecting filtrate fluid into theport 111D when the transverse filter resistance characteristic exceeds(e.g., is less than) a second filter resistance threshold. Accordingly,the performance of the blood filtration system 500 is improved because alifetime of the filter 110 can be extended by reducing clogging of thefilter 110.

FIG. 6 shows a flowchart for a second method 600 for preserving a filterfor a blood filtration system. In describing the method 600, referenceis made to one or more components, features, functions and operationspreviously described herein. Where convenient, reference is made to thecomponents, features, operations and the like with reference numerals.The reference numerals provided are exemplary and are not exclusive. Forinstance, components, features, functions, operations and the likedescribed in the method 600 include, but are not limited to, thecorresponding numbered elements provided herein and other correspondingelements described herein (both numbered and unnumbered) as well astheir equivalents. Additionally, the method 600 can be included ininstructions on a computer readable medium, and the instructions can becarried out by the controller 102 (e.g., processing circuitry).

At operation 610, a filter resistance can be determined. In someexamples, the controller 102 compares pressure at the inlet pressuresensor 590A or the filtration pressure sensor 590C to an outlet pressuresensor 590B or a harvesting pressure sensor 590D to determine the filterresistances, or to improve the accuracy of the filter resistancedeterminations. In an example, the transverse filter resistance can becalculated according to the pressure differential between the outletpressure sensor 590B and the filtration pressure sensor 590C, anddividing the pressure differential by the flow rate of the filtrationpump (e.g., the filtration pump 116 shown in FIG. 1). In anotherexample, the longitudinal filter resistance can be calculated accordingto the pressure differential between the inlet pressure sensor 590A andthe filtration pressure sensor 590C, and dividing the pressuredifferential by the flow rate of the blood pump (e.g., the blood pump112 shown in FIG. 1).

At operation 620, the blood flow rate can be determined, for instance bydetermining the operating rate of the blood pump 112, shown in FIG. 1.At operation 630, the controller 102 can determine if the blood flowrate is intermittent (e.g., varying, fluctuating, or the like) andaccordingly the controller 102 can operate the filtration pump 116(e.g., stop the filtration pump) and operate the harvesting pump 220(e.g., operate the harvesting pump 220 to inject filtrate fluid into theharvesting port 111D). Additionally, the controller can determine if oneor more filter resistances are greater than a filter resistancethreshold and accordingly the controller 102 can operate the filtrationpump 116 and operate the harvesting pump 220. Additionally, thecontroller 102 can monitor the blood flow rate over time (e.g., bydetermining the blood flow rate with the one or more sensors 124), andwhen the blood flow rate decreases over time below a blood flow ratethreshold, the controller 102 can operate the filtration pump 116 andoperate the harvesting pump 220. Accordingly, the method 600 can reduceclogging in the filter and improve the performance of a blood filtrationsystem.

FIG. 7 shows a schematic view of a fifth blood filtration system 700.The blood filtration system can include on or more filters 110, forinstance a first filter 110A or a second filter 110B. In an example, andas shown in FIG. 7, the filters 110A, 110B can be arranged in parallel.In another example, the filters 110A, 110B can be arranged in series.The blood filtration system can include a first valve 710A and caninclude a second valve 710B. The valves 710A, 710B can facilitate theflow of fluids (e.g., blood or filtrate fluid) through the system 500.

In an example, the valve 710A can be configured to divert blood flowthrough the filter 110A or the filter 110B. For instance, the valve 710Acan be operated (e.g., by a user, or the controller 102, for examplewith a control signal) to divert the flow of blood between the filters110A, 110B. In another example, the valve 710B can be operated (e.g., bya user, or the controller 102, for example with a control signal) todivert the facilitate the extraction of filtrate fluid from the filters110A, 110B.

FIG. 8A shows a schematic view of a sixth blood filtration system 800.The blood filtration system 800 can include an agitator 810 coupled withthe filter 110. In an example, the agitator 810 can provide vibrationsto the filter 110. In an example, the agitator 810 can include apiezoelectric element, and the agitator 810 can be operated by thecontroller 102 (e.g., with a control signal, for instance a controlsignal in communication with a relay that energizes the piezoelectricelement). In another example, the agitator 810 can include an ultrasoundgenerator that in some examples is operated by the controller 102.

The agitator 810 can reduce clogging in the filter 110, for instancewhen blood clots in the filter 110. In an example, the controller 102can operate the agitator 810 when a filter resistance (e.g., thelongitudinal filter resistance) exceeds a filter resistance threshold(e.g., the first filter resistance threshold). Accordingly, the agitator810 can improve the performance of the blood filtration system 800, forinstance by providing a vibration to the filter 110 and thereby reducingclotting of blood within the filter 110.

As shown in FIG. 8B, the filter 110 can have a variable volume. In anexample, a filter cap 820 can be operated (e.g., rotated, turned,twisted, engaged with, or the like) and the volume of the filter 110 cancorrespondingly vary. For instance, operation of the filter cap canchange the dimension of an aperture 830 (e.g., by changing a dimensionof an iris mechanism, a Tuohy Borst mechanism, or the like). Changingthe dimension of the aperture 830 can block one or more portions of thefilter, for instance filter fibers 840, and change the volume of thefilter 110. In some examples, the volume of the filter 110 is adjustedto meet patient needs. For instance, a child can have its blood filteredby the blood filtration system 800, and the volume of the filter 110 canbe adjusted to accommodate for the reduced stature of the child. Thevariable volume of the filter 110 allows for a filter to have a variablefiltration capacity (e.g., the amount of filtrate fluid that isextracted by the filter 110), and accordingly improves the performanceof the blood filtration system 800.

FIG. 9 shows a schematic view of a seventh blood filtration system 900.The blood filtration system 900 can include a system housing 910 thatincludes controls 920 (e.g., buttons) that can change various operatingparameters of the system 900, for instance a button that operates theblood pump 112 (shown in FIG. 1). The system housing 910 can include thecontroller 102, and the controls 920 can communicate with the controller102 to operate one or more components of the blood filtration system(e.g., the harvesting pump 220 shown in FIG. 2).

The blood filtration system 900 can include an optical sensor 930 (e.g.,a camera, an infrared camera, or the like) that can monitor movement ofthe patient, for instance my observing a patient reference point 940(e.g., a head of the patient, a mark included on a surface of an objectsecured to the patient, for instance a blood pressure cuff, or thelike). The optical sensor 930 can monitor the position of the patientreference point and the controller 102 can be configured to determine ifmovement of the patient from an initial position affects the determinedhematocrit value of the patient. The hematocrit value determination canbe affected by movement of a patient, for example when the patienttransitions from a supine position (e.g., laying down) to a standingposition.

In an example, the controller 102 can be configured to provide anotification if the hematocrit determination is affected by the movementof the patient. For instance, the controller 102 can provide anotification on a display 950 with a timer indicating the time since thepatient moved in a way that affected the hematocrit value determination.In an example, the controller 102 can compare the change in position ofthe portion of the body of the patient to a positional threshold andprovide a notification when the change in position exceeds thepositional threshold. For instance, the controller 102 can determine theposition of the patient reference point 940 relative to the opticalsensor 930.

In yet another example, the controller 102 can operate a speaker andchange a tone according to the patient movement (e.g., initiate a beepif the patient moves). Additionally, the controller 102 can determine amovement value for instance a difference between the position of thepatient reference point to the initial position. Further, the controllercan compare the movement value to a movement threshold and can provide anotification if the movement value exceeds the movement threshold.

In another example, the controller 102 can refrain from providing anotification of the hematocrit value when the hematocrit value isaffected by movement of the patient (e.g., by refraining from displayingthe movement-affected hematocrit value on the display 950). Accordingly,the blood filtration system 900 can provide additional information(e.g., to a healthcare provider) that the hematocrit value of thepatient has been affected by movement of the patient.

In yet another example, the patient reference point 940 can include anaccelerometer, and the accelerometer can be in communication with thecontroller 102 (e.g., with a wired or wireless communication pathway).The accelerometer can monitor the movement of the patient by determiningacceleration of a portion of a body of the patient (e.g., an arm). Thecontroller 102 can determine if the movement of the patient from theinitial position affects the determined hematocrit value of the patient,for instance by comparing the acceleration of the portion of the body ofthe patient to an acceleration threshold.

In still yet another example, a pressure sensor in communication with ablood stream of the patient (e.g., the first sensor 124A or the secondsensor 124B shown in FIG. 1) can monitor a change in pressure within theblood stream of the patient. The controller 102 can determine if themovement of the patient from the initial position affects the determinedhematocrit value of the patient, for instance by comparing the change inpressure (e.g., because the patient transitioned from laying down tostanding) within the blood stream to a pressure threshold. Thecontroller 102 can provide a notification if the change in pressureexceeds the pressure threshold.

In some examples, the controller 102 can apply a correction value to thedetermined hematocrit value of the patient according to the movement ofthe patient. For instance, the correction value can be determined byevaluating a change in the hematocrit value according to the motion ofthe patient. The controller 102 can log data associated with changes inpatient position and corresponding changes in hematocrit values todetermine the correction value.

FIG. 10 shows a schematic view of an eighth blood filtration system1000. The blood filtration system 1000 can include a proximal venousocclusion cuff 1010 and can include a distal venous occlusion cuff 1020.The cuffs 1010, 1020 can engage with an arm of the patient to encourageblood flow in the arm of the patient. In an example, the controller 102can operate the cuffs 1010, 1020 to constrict the cuff 1010 or the cuff1020. Constricting the cuffs 1010, 1020 can cause the blood pressure inthe arm to increase. The controller 102 can operate the cuff 1010 toloosen the cuff 1010, or the 1020, which can encourage blood flow in thearm, for instance by increasing blood flow into the catheter 108 (shownin FIG. 1).

The controller 102 can operate the cuffs 1010, 1020 to synchronize thecuffs 1010, 1020. In an example, the controller 102 can operate thecuffs 1010, 1020 to tighten the cuffs 1010, 1020 at the same point intime. In another example, the controller 102 can operate the cuffs 1010,1020 to loosen the cuffs 1010, 1020 at the same point in time. In yetanother example, the controller 102 can operate the cuffs 1010, 1020 totighten the cuff 1010, while the cuff 1020 is loosened. In still yetanother example, the controller 102 can operate the cuffs 1010, 1020 totighten the cuff 1020, while the cuff 1010 is loosened.

FIGS. 11A-11B are photographs of line protectors 1100 for a bloodfiltration system. The line protectors 1100 can be located around lines(e.g., the lines 104, 106, 114, 210 shown in FIG. 2, or the like) of ablood filtration system (e.g., the blood filtration system 100, shown inFIG. 1). The protectors 1100 can prevent compression of the lines of theblood filtration system and accordingly ensure flow of fluid (e.g.,blood or filtrate fluid) through the lines.

FIG. 12 illustrates a block diagram of an example machine 1200 uponwhich any one or more of the techniques (e.g., methodologies) discussedherein can perform, for instance the controller 102. Examples, asdescribed herein, can include, or can operate by, logic or a number ofcomponents, or mechanisms in the machine 1200. Circuitry (e.g.,processing circuitry) is a collection of circuits implemented intangible entities of the machine 1200 that include hardware (e.g.,simple circuits, gates, logic, etc.). Circuitry membership can beflexible over time. Circuitries include members that may, alone or incombination, perform specified operations when operating. In an example,hardware of the circuitry can be immutably designed to carry out aspecific operation (e.g., hardwired). In an example, the hardware of thecircuitry can include variably connected physical components (e.g.,execution units, transistors, simple circuits, etc.) including a machinereadable medium physically modified (e.g., magnetically, electrically,moveable placement of invariant massed particles, etc.) to encodeinstructions of the specific operation. In connecting the physicalcomponents, the underlying electrical properties of a hardwareconstituent are changed, for example, from an insulator to a conductoror vice versa. The instructions enable embedded hardware (e.g., theexecution units or a loading mechanism) to create members of thecircuitry in hardware via the variable connections to carry out portionsof the specific operation when in operation. Accordingly, in an example,the machine readable medium elements are part of the circuitry or arecommunicatively coupled to the other components of the circuitry whenthe device is operating. In an example, any of the physical componentscan be used in more than one member of more than one circuitry. Forexample, under operation, execution units can be used in a first circuitof a first circuitry at one point in time and reused by a second circuitin the first circuitry, or by a third circuit in a second circuitry at adifferent time. Additional examples of these components with respect tothe machine 1200 follow.

In alternative embodiments, the machine 1200 can operate as a standalonedevice or can be connected (e.g., networked) to other machines. In anetworked deployment, the machine 1200 can operate in the capacity of aserver machine, a client machine, or both in server-client networkenvironments. In an example, the machine 1200 can act as a peer machinein peer-to-peer (P2P) (or other distributed) network environment. Themachine 1200 can be a personal computer (PC), a tablet PC, a set-top box(STB), a personal digital assistant (PDA), a mobile telephone, a webappliance, a network router, switch or bridge, or any machine capable ofexecuting instructions (sequential or otherwise) that specify actions tobe taken by that machine. Further, while only a single machine isillustrated, the term “machine” shall also be taken to include anycollection of machines that individually or jointly execute a set (ormultiple sets) of instructions to perform any one or more of themethodologies discussed herein, such as cloud computing, software as aservice (SaaS), other computer cluster configurations.

The machine (e.g., computer system) 1200 can include a hardwareprocessor 1202 (e.g., a central processing unit (CPU), a graphicsprocessing unit (GPU), a hardware processor core, or any combinationthereof), a main memory 1204, a static memory (e.g., memory or storagefor firmware, microcode, a basic-input-output (BIOS), unified extensiblefirmware interface (UEFI), etc.) 1206, and mass storage 1208 (e.g., harddrive, tape drive, flash storage, or other block devices) some or all ofwhich can communicate with each other via an interlink (e.g., bus) 1230.The machine 1200 can further include a display unit 1210, analphanumeric input device 1212 (e.g., a keyboard), and a user interface(UI) navigation device 1214 (e.g., a mouse). In an example, the displayunit 1210, input device 1212 and UI navigation device 1214 can be atouch screen display. The machine 1200 can additionally include astorage device (e.g., drive unit) 1208, a signal generation device 1218(e.g., a speaker), a network interface device 1220, and one or moresensors 1216, such as a global positioning system (GPS) sensor, compass,accelerometer, or other sensor. The machine 1200 can include an outputcontroller 1228, such as a serial (e.g., universal serial bus (USB),parallel, or other wired or wireless (e.g., infrared (IR), near fieldcommunication (NFC), etc.) connection to communicate or control one ormore peripheral devices (e.g., a printer, card reader, etc.).

Registers of the processor 1202, the main memory 1204, the static memory1206, or the mass storage 1208 can be, or include, a machine readablemedium 1222 on which is stored one or more sets of data structures orinstructions 1224 (e.g., software) embodying or utilized by any one ormore of the techniques or functions described herein. The instructions1224 can also reside, completely or at least partially, within any ofregisters of the processor 1202, the main memory 1204, the static memory1206, or the mass storage 1208 during execution thereof by the machine1200. In an example, one or any combination of the hardware processor1202, the main memory 1204, the static memory 1206, or the mass storage1208 can constitute the machine readable media 1222. While the machinereadable medium 1222 is illustrated as a single medium, the term“machine readable medium” can include a single medium or multiple media(e.g., a centralized or distributed database, and/or associated cachesand servers) configured to store the one or more instructions 1224.

The term “machine readable medium” can include any medium that iscapable of storing, encoding, or carrying instructions for execution bythe machine 1200 and that cause the machine 1200 to perform any one ormore of the techniques of the present disclosure, or that is capable ofstoring, encoding or carrying data structures used by or associated withsuch instructions. Non-limiting machine readable medium examples caninclude solid-state memories, optical media, magnetic media, and signals(e.g., radio frequency signals, other photon based signals, soundsignals, etc.). In an example, a non-transitory machine readable mediumcomprises a machine readable medium with a plurality of particles havinginvariant (e.g., rest) mass, and thus are compositions of matter.Accordingly, non-transitory machine-readable media are machine readablemedia that do not include transitory propagating signals. Specificexamples of non-transitory machine readable media can include:non-volatile memory, such as semiconductor memory devices (e.g.,Electrically Programmable Read-Only Memory (EPROM), ElectricallyErasable Programmable Read-Only Memory (EEPROM)) and flash memorydevices; magnetic disks, such as internal hard disks and removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks.

The instructions 1224 can be further transmitted or received over acommunications network 1226 using a transmission medium via the networkinterface device 1220 utilizing any one of a number of transferprotocols (e.g., frame relay, internet protocol (IP), transmissioncontrol protocol (TCP), user datagram protocol (UDP), hypertext transferprotocol (HTTP), etc.). Example communication networks can include alocal area network (LAN), a wide area network (WAN), a packet datanetwork (e.g., the Internet), mobile telephone networks (e.g., cellularnetworks), Plain Old Telephone (POTS) networks, and wireless datanetworks (e.g., Institute of Electrical and Electronics Engineers (IEEE)802.11 family of standards known as Wi-Fi®, IEEE 802.16 family ofstandards known as WiMax®), IEEE 802.15.4 family of standards,peer-to-peer (P2P) networks, among others. In an example, the networkinterface device 1220 can include one or more physical jacks (e.g.,Ethernet, coaxial, or phone jacks) or one or more antennas to connect tothe communications network 1226. In an example, the network interfacedevice 1220 can include a plurality of antennas to wirelesslycommunicate using at least one of single-input multiple-output (SIMO),multiple-input multiple-output (MIMO), or multiple-input single-output(MISO) techniques. The term “transmission medium” shall be taken toinclude any intangible medium that is capable of storing, encoding orcarrying instructions for execution by the machine 1200, and includesdigital or analog communications signals or other intangible medium tofacilitate communication of such software. A transmission medium is amachine readable medium.

One or more of components, features, functions, or the like of the bloodfiltration systems (e.g., the blood filtration systems 100, 200, 400,500, 700, 800, 900, 1000) described herein can be combined into one ormore combinations, or sub-combinations. Additionally, one or moreconfigurations of the controller 102 can be combined into or morecombinations, or sub-combinations. Further, one or more configurations,techniques, or functions associated with the controller 102 can beincluded in a machine readable medium on which is stored one or moresets of data structures or instructions (e.g., software) embodying orutilized by any one or more of the techniques or functions describedherein.

FIG. 13 shows a graph of a filtration fraction of a blood filtrationsystem versus a hematocrit level of a patient. As discussed herein, thehematocrit of the patient is determined according to Equation (1), andthe filtration fraction of a blood filtration system is determinedaccording to Equation (2). A blood filtration system (e.g., the bloodfiltration system 100 shown in FIG. 1) can include a hematocritthreshold 1300 (e.g., 50 percent, or within a range of 45 percent to 55percent, or the like). Additionally, the blood filtration system caninclude a filtration fraction threshold 1310. In some examples, if thehematocrit threshold 1300, or the filtration fraction threshold 1310 areexceeded, a filter (e.g., the filter shown in FIG. 1) can becomeclogged, for instance due to blood clotting in the filter. Accordingly,the blood filtration system can be operated (e.g., by the controller102) to maintain the filtration fraction below the filtration fractionthreshold 1310, and can maintain a patient hematocrit value less thanthe hematocrit threshold 1300.

In an example, the filtration pump 116 (shown in FIG. 1) can be operatedto vary a speed of the filtration pump (e.g., between 10-500 millilitersper hour). The speed of the filtration pump 116 can be variedincrementally (e.g., in 5 millimeter per hour increments). Thecontroller 102 can operate the filtration pump 116 to vary the speed ofthe filtration pump 116, and accordingly maintain the filtrationfraction below the filtration fraction threshold 1310. Additionally, thecontroller 102 can operate the blood pump 112 (shown in FIG. 1) tomaintain the filtration fraction below the filtration fraction threshold1310 (e.g., by varying the blood flow rate through the system). Further,the controller 102 can stop the filtration pump 116 (e.g., to stoptherapy with the blood filtration system) if the hematocrit threshold1300 is exceeded.

In an example, the blood filtration system can extract filtrate fluid ata high filtration rate (e.g., 400 milliliters per hour), as shown by afirst curve 1320. As filtrate fluid is extracted from the patient, thehematocrit level of the patient increases, and the filtration fractionincreases (because the denominator of Equation (1) is reduced). Theblood filtration system can maintain the high filtration rate until thefiltration fraction threshold 1310 is exceeded, and the blood filtrationsystem can operate the filtration pump 116 at an intermediate filtrationrate (e.g., 200 milliliters per hour), as shown by a second curve 1330.The blood filtration system can continue to extract filtrate fluid fromblood of the patient at the intermediate filtration rate, andaccordingly the hematocrit value of the patient can continue toincrease. Accordingly, the filtration fraction continues to increase atthe intermediate filtration rate. The blood filtration system canmaintain the intermediate filtration rate until the filtration fractionthreshold 1310 is exceeded.

Once the filtration fraction 1310 has been exceeded at the intermediatefiltration rate, the blood filtration system can operate the filtrationpump at a low filtration rate (e.g., 50 milliliters per hour), as shownby a third curve 1340. The blood filtration system can continue toextract filtrate fluid from blood of the patient at the low filtrationrate, and accordingly the hematocrit value of the patient can continueto increase. The blood filtration system can maintain the low filtrationrate until the hematocrit threshold 1300 is exceeded, and the bloodfiltration system can stop the filtration pump 116 (e.g., a filtrationrate of 0 milliliters per second).

Once the hematocrit threshold 1300 has been exceeded, the blood pump 112can continue to pump blood through the blood filtration system, and theblood filtration system can monitor the hematocrit value (or otherhealth parameters of the patient) to determine if the patient requiresadditional therapy (e.g., extraction of filtrate fluid from the blood).For instance, the plasma refill rate of the patient can reduce thehematocrit value of the patient, and blood filtration system can resumetherapy.

FIG. 14 shows a method 1400 for determining venous pressure of a patientwith a blood filtration system (e.g., the blood filtration system 100,or the like). In describing the method 300, reference is made to one ormore components, features, functions and operations previously describedherein. Where convenient, reference is made to the components, features,operations and the like with reference numerals. The reference numeralsprovided are exemplary and are not exclusive. For instance, components,features, functions, operations and the like described in the method1400 include, but are not limited to, the corresponding numberedelements provided herein and other corresponding elements describedherein (both numbered and unnumbered) as well as their equivalents.Additionally, the method 1400 can be included in instructions on acomputer readable medium, and the instructions can be carried out by thecontroller 102 (e.g., processing circuitry).

At 1410, the method 1400 can include determining a hematocrit value of apatient, for example with the controller 102 (e.g., the controller 102can communicate with the hematocrit sensor 126 to determine thehematocrit value). The method 1400 can include at 1420 that the bloodpump 112 can be operated to stop a flow of blood in the blood circuit140 (e.g., within the lines 104, 106).

At 1430, a pressure head in a component of the blood circuit 140 (e.g.,one or more of the lines 104, 106, the catheter 108, or the like) can becompensated for when determining the venous pressure of the patient. Forexample, at 1440 an elevation difference between the catheter tip 130and a pressure sensor (e.g., the sensor 124A) can be determined, forexample with the system 100 (e.g., the controller 102 in communicationwith one or more position sensors). In another example, at 1450 anelevation difference between a pressure sensor (e.g., the sensor 124A)and a position sensor (e.g., the sensor 124D) can be determined (e.g.,by determining the difference in elevation between the sensors 124A,124D with the controller 102).

At 1460, a density of the blood of the patient can be determined. Thedetermined head pressure in the blood circuit can correspond to (e.g., avariable in an equation that determines the head pressure, associatedwith, contribute to, based on, or the like) the density of the blood ofthe patient. Accordingly, determining the blood density can improve theaccuracy of the head pressure compensation when determining the venouspressure of the patient.

At 1470, the method 1400 can include determining the pressure (e.g.,with the sensors 124A, 124B) in a component of the blood circuit 140,for example the withdrawal line 104 or the infusion line 106. In anexample, the catheter tip 130 is located within vasculature of thepatient, and the system 100 can withdraw blood from (or infuse bloodinto) the vasculature of the patient. Accordingly, when the blood pump112 is operated to stop the flow of blood in the blood circuit 140, thepressure in the lines 104, 106 can correspond to the pressure in thevasculature of the patient. As a result, the system 100 can determinethe venous pressure in the vasculature of the patient with the sensors124.

VARIOUS NOTES

Aspect 1 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: avariable-speed blood pump configured to pump blood in a withdrawal line,through a filter, and into an infusion line, wherein: the withdrawalline and the infusion line are configured to couple with a catheter, andthe catheter is configured for insertion into a blood stream of thepatient; the withdrawal line and the infusion line are configured tocouple with the filter, and the filter is configured to reduce an amountof one or more plasma constituents in blood flowing through the filterand provide a filtrate fluid including the plasma constituents; avariable speed filtration pump configured to extract the filtrate fluidfrom the filter; and a controller including processing circuitry,wherein the controller is configured to: control the speed of the bloodpump to vary a flow rate of the blood through the filter; control thespeed of the filtration pump to vary the extraction rate of the filtratefluid from the filter; determine a venous pressure of the patient; andprovide a notification of the venous pressure of the patient.

In Aspect 2, the subject matter of Aspect 1 optionally includes whereindetermining the venous pressure of the patient includes controlling thespeed of the blood pump to stop the blood pump.

In Aspect 3, the subject matter of Aspect 2 optionally includes a firstpressure sensor in communication with the withdrawal line and a secondpressure sensor in communication with the infusion line, whereindetermining the venous pressure of the patient includes determining apressure differential between the first pressure sensor and the secondpressure sensor, and providing the notification when the pressuredifferential exceeds a pressure differential threshold.

In Aspect 4, the subject matter of any one or more of Aspects 1-3optionally include wherein the controller is configured to determine ahematocrit value of the patient, and the controller is furtherconfigured to set the extraction rate of filtrate fluid from the filterusing the determined hematocrit value of the patient.

In Aspect 5, the subject matter of Aspect 4 optionally includes whereindetermining the hematocrit value of the patient includes: controllingthe speed of the blood pump and setting the flow rate of blood throughthe filter at a first blood flow rate; controlling the speed of theblood pump and setting the flow rate of blood through the filter at asecond blood flow rate, wherein the first blood flow rate is differentthan the second blood flow rate; and determining the hematocrit at thesecond blood flow rate.

In Aspect 6, the subject matter of Aspect 5 optionally includes whereindetermining the hematocrit value of the patient includes controlling thespeed of the pump and setting the flow rate of blood through the filterat the first rate after determining the hematocrit value of the patient.

In Aspect 7, the subject matter of any one or more of Aspects 4-6optionally include wherein the controller is configured to determine ared blood cell volume of the blood of the patient using the hematocritvalue of the patient.

In Aspect 8, the subject matter of Aspect 7 optionally includes whereindetermining the red blood cell volume of the blood of the patientincludes: controlling a speed of the filtration pump by changing afiltration rate from a first filtration rate to a second filtrationrate; determining a first rate of change of an inverse of the hematocritvalue of the patient corresponding to the hematocrit value of thepatient at the first filtration rate; determining a second rate ofchange of an inverse of the hematocrit value of the patientcorresponding to the hematocrit value of the patient at the secondfiltration rate; and determining a difference between the first rate ofchange and the second rate of change.

In Aspect 9, the subject matter of any one or more of Aspects 7-8optionally include wherein the controller is configured to: determine afiltrate fluid extraction volume corresponding to a volume of filtratefluid extracted from the patient, wherein the filtrate fluid extractionvolume is determined using the determined red blood cell volume; anddetermine a plasma refill rate of the patient according to thedetermined hematocrit value of the patient and the determined filtratefluid extraction volume.

In Aspect 10, the subject matter of any one or more of Aspects 1-9optionally include wherein determining the venous pressure of thepatient includes compensating for a pressure head in the withdrawal lineor the infusion line.

In Aspect 11, the subject matter of Aspect 10 optionally includes afirst pressure sensor in communication with the withdrawal line andconfigured to measure the pressure in the withdrawal line, wherein thefirst pressure sensor is located remote from a catheter tip of thewithdrawal line, and the controller is configured to determine thevenous pressure of the patient at the catheter tip by compensating forthe pressure head in the withdrawal line between the catheter tip andthe first pressure sensor.

In Aspect 12, the subject matter of any one or more of Aspects 1-11optionally include a blood circuit configured to couple with the bloodfiltration system, the blood circuit including the catheter, thewithdrawal line, and infusion line; an activation key coupled with aportion of the blood circuit, wherein the activation key is incommunication with the controller, and the controller provides anactivated characteristic to the activation key when the blood circuit iscoupled to the blood filtration system.

In Aspect 13, the subject matter of Aspect 12 optionally includeswherein the controller is configured to provide an expirationcharacteristic to the activation key after a specified time period fromwhen the controller provided the activated characteristic to theactivation key, and providing the activation key with the expirationcharacteristic inhibits operation of the blood filtration system.

Aspect 14 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: avariable-speed blood pump configured to pump blood in a withdrawal line,through a filter, and into an infusion line, wherein: the withdrawalline and the infusion line are configured to couple with a catheter, andthe catheter is configured for insertion into a blood stream of thepatient; a controller including processing circuitry, wherein thecontroller is configured to: determine a withdrawal line resistancecharacteristic of the withdrawal line using a first pressure sensor incommunication with the withdrawal line, the withdrawal line resistancecharacteristic corresponding to an amount of resistance to a flow ofblood through the withdrawal line; determine an infusion line resistancecharacteristic of the infusion line using a second pressure sensor incommunication with the infusion line, the infusion line resistancecharacteristic corresponding to an amount of resistance to a flow ofblood through the infusion line; and provide a notification of one ormore of the withdrawal line resistance characteristic or the infusionline resistance characteristic.

In Aspect 15, the subject matter of Aspect 14 optionally includeswherein the controller is configured to: determine a hematocrit value ofthe patient; determine a hemoconcentration resistance characteristic ofthe blood according to the determined hematocrit value of the patient,wherein the withdrawal line resistance characteristic or the infusionline resistance characteristic correspond in part to thehemoconcentration characteristic; and determine an occlusion resistancecharacteristic by subtracting the hemoconcentration resistancecharacteristic from the withdrawal line resistance characteristic orfrom the infusion line resistance characteristic.

In Aspect 16, the subject matter of Aspect 15 optionally includeswherein the notification of the one or more of the withdrawal lineresistance characteristic or the infusion line resistance characteristicincludes the occlusion resistance characteristic.

In Aspect 17, the subject matter of any one or more of Aspects 15-16optionally include wherein the controller is configured to provide anotification of the occlusion resistance characteristic.

In Aspect 18, the subject matter of any one or more of Aspects 15-17optionally include wherein determining the hematocrit value of thepatient includes: controlling the speed of the blood pump and setting aflow rate of blood through the filter at a first blood flow rate;controlling the speed of the blood pump and setting the flow rate ofblood through the filter at a second blood flow rate, wherein the firstblood flow rate is different than the second blood flow rate; anddetermining the hematocrit at the second blood flow rate.

In Aspect 19, the subject matter of any one or more of Aspects 14-18optionally include wherein the controller is configured to: compare theinfusion line resistance or the withdrawal line resistance to aresistance threshold; reduce a filtration rate or increase the bloodflow rate if the withdrawal line resistance or the infusion lineresistance exceeds the resistance threshold.

In Aspect 20, the subject matter of any one or more of Aspects 14-19optionally include wherein the withdrawal line and the infusion line areconfigured to be in communication with the filter, and the filter isconfigured to reduce an amount of one or more plasma constituents inblood flowing through the filter and provide a filtrate fluid includingthe plasma constituents.

In Aspect 21, the subject matter of Aspect 20 optionally includeswherein the controller is further configured to: control the speed of afiltration pump to vary the extraction rate of the filtrate fluid fromthe filter; vary the extraction rate from a first specified extractionrate; wait for a specified time period; monitor the withdrawal lineresistance characteristic or the infusion line resistancecharacteristic; and provide a notification if the infusion lineresistance characteristic or the withdrawal line resistancecharacteristic increases after the specified time period.

In Aspect 22, the subject matter of any one or more of Aspects 20-21optionally include wherein the controller is configured to: vary afiltration rate for reducing the plasma constituents in the blood; waitfor a specified time period; monitor the withdrawal line resistance orthe infusion line resistance, and operate a harvesting pump to extractfiltrate fluid from a filtrate reservoir and inject the filtrate fluidinto an inlet of the filter to dilute the blood flowing through thefilter.

In Aspect 23, the subject matter of any one or more of Aspects 14-22optionally include wherein the controller is configured to: determine avenous pressure of the patient by determining a pressure differentialbetween the first pressure sensor and the second pressure sensor; andprovide a notification when the pressure differential exceeds a pressuredifferential threshold.

In Aspect 24, the subject matter of Aspect 23 optionally includeswherein determining the venous pressure of the patient includescompensating for a pressure head in the withdrawal line.

In Aspect 25, the subject matter of Aspect 24 optionally includes afirst pressure sensor in communication with the withdrawal line andconfigured to measure the pressure in the withdrawal line, wherein thefirst pressure sensor is located remote from a catheter tip of thewithdrawal line, and the controller is configured to determine thevenous pressure of the patient at the catheter tip by compensating forthe pressure head in the withdrawal line between the catheter tip andthe first pressure sensor.

In Aspect 26, the subject matter of any one or more of Aspects 14-25optionally include wherein the controller is further configured todetermine a blood flow rate of the blood flowing through the filter.

Aspect 27 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: a controllerincluding processing circuitry, wherein the controller is configured to:determine a filter resistance of a filter, wherein the filter isconfigured to reduce an amount of one or more plasma constituents inblood flowing through the filter and provide a filtrate fluid includingthe plasma constituents; determine if the filter resistance of thefilter exceeds a first filter resistance threshold; operate a harvestingpump to extract filtrate fluid from a filtrate reservoir and inject thefiltrate fluid into an inlet of the filter to dilute the blood flowingthrough the filter; monitor the filter resistance of the filter; andoperate the harvesting pump to stop injecting filtrate fluid into theinlet of the filter when the filter resistance exceeds a second filterresistance threshold.

In Aspect 28, the subject matter of Aspect 27 optionally includeswherein the controller is further configured to determine a blood flowrate of the blood flowing through the filter.

In Aspect 29, the subject matter of Aspect 28 optionally includeswherein the controller is further configured to: determine if the bloodflow rate exceeds a first flow rate threshold; operate the harvestingpump to inject filtrate fluid into the inlet of the filter; monitor theblood flow rate; and operate the harvesting pump to stop injectingfiltrate fluid into the inlet of the filter when the blood flow rateexceeds a second flow rate threshold.

In Aspect 30, the subject matter of any one or more of Aspects 27-29optionally include wherein the controller is further configured to:monitor a rate of change of the filter resistance; compare the rate ofchange of the filter resistance to a rate of change threshold.

In Aspect 31, the subject matter of any one or more of Aspects 27-30optionally include wherein the controller is configured to: determine awithdrawal line resistance characteristic of the withdrawal line using afirst pressure sensor in communication with the withdrawal line, thewithdrawal line resistance characteristic corresponding to an amount ofresistance to a flow of blood through the withdrawal line; determine aninfusion line resistance characteristic of the infusion line using asecond pressure sensor in communication with the infusion line, theinfusion line resistance characteristic corresponding to an amount ofresistance to a flow of blood through the infusion line; and provide anotification of one or more of the withdrawal line resistancecharacteristic or the infusion line resistance characteristic.

In Aspect 32, the subject matter of Aspect 31 optionally includeswherein the controller is configured to: determine a hematocrit value ofthe patient; determine a hemoconcentration resistance characteristic ofthe blood according to the determined hematocrit value of the patient,wherein the withdrawal line resistance characteristic or the infusionline resistance characteristic correspond in part to thehemoconcentration characteristic; and determine an occlusion resistancecharacteristic by subtracting the hemoconcentration resistancecharacteristic from the withdrawal line resistance characteristic orfrom the infusion line resistance characteristic.

In Aspect 33, the subject matter of Aspect 32 optionally includeswherein the notification of the one or more of the withdrawal lineresistance characteristic or the infusion line resistance characteristicincludes the occlusion resistance characteristic.

In Aspect 34, the subject matter of any one or more of Aspects 32-33optionally include wherein the controller is configured to provide anotification of the occlusion resistance characteristic.

In Aspect 35, the subject matter of any one or more of Aspects 32-34optionally include wherein determining the hematocrit value of thepatient includes: controlling a speed of the blood pump and setting aflow rate of blood through the filter at a first blood flow rate;controlling the speed of the blood pump and setting the flow rate ofblood through the filter at a second blood flow rate, wherein the firstblood flow rate is different than the second blood flow rate; anddetermining the hematocrit at the second blood flow rate.

In Aspect 36, the subject matter of any one or more of Aspects 31-35optionally include wherein the controller is configured to: compare theinfusion line resistance or the withdrawal line resistance to aresistance threshold; reduce a filtration rate or increase a blood flowrate if the withdrawal line resistance or the infusion line resistanceexceeds the resistance threshold.

Aspect 37 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: a firstsensor configured to determine a hematocrit value of the patient; asecond sensor configured to monitor movement of the patient relative toan initial position of the patient, a controller including processingcircuitry, wherein the controller is configured to: monitor thehematocrit value of the patient, determine if the movement of thepatient from the initial position affects the determined hematocritvalue of the patient; and provide a notification if the hematocritdetermination is affected by the movement of the patient.

In Aspect 38, the subject matter of Aspect 37 optionally includeswherein: the first sensor includes an accelerometer coupled with thepatient, and the accelerometer is configured to monitor the movement ofthe patient by determining acceleration of a portion of a body of thepatient; and determining if the movement of the patient from the initialposition affects the determined hematocrit value of the patient includescomparing the acceleration of the portion of the body of the patient toan acceleration threshold.

In Aspect 39, the subject matter of any one or more of Aspects 37-38optionally include wherein: the first sensor includes an accelerometercoupled with the patient, and the accelerometer is configured to monitorthe movement of the patient by determining a change in position of aportion of a body of the patient; and determining if the movement of thepatient from the initial position affects the determined hematocritvalue of the patient includes comparing the change in position of theportion of the body of the patient to a positional threshold.

In Aspect 40, the subject matter of any one or more of Aspects 37-39optionally include wherein: the first sensor includes an optical sensorcoupled with the blood filtration system, and the optical sensor isconfigured to monitor the movement of the patient by observing a patientreference point; and determining if the movement of the patient from theinitial position affects the determined hematocrit value of the patientincludes: determining the position of the patient reference pointrelative to the optical sensor; determining a movement value, whereinthe movement value is equal to a difference between the position of thepatient reference point to the initial position; and comparing themovement value to a movement threshold.

In Aspect 41, the subject matter of any one or more of Aspects 37-40optionally include wherein: the first sensor includes a pressure sensorin communication with a blood stream of the patient, and the firstsensor is configured to monitor a change in pressure within the bloodstream of the patient; determining if the movement of the patient fromthe initial position affects the determined hematocrit value of thepatient includes comparing the change in pressure within the bloodstream with a pressure threshold.

In Aspect 42, the subject matter of any one or more of Aspects 37-41optionally include wherein the controller is further configured to applya correction value to the determined hematocrit value according to themovement of the patient, wherein the correction value is determined byevaluating a change in the hematocrit value according to motion of thepatient.

In Aspect 43, the subject matter of any one or more of Aspects 37-42optionally include wherein the controller is configured to determine avenous pressure of the patient using the hematocrit value of thepatient, and determining the venous pressure of the patient includescompensating for a pressure head in a withdrawal line or an infusionline.

In Aspect 44, the subject matter of Aspect 43 optionally includes afirst pressure sensor in communication with the withdrawal line andconfigured to measure the pressure in the withdrawal line, wherein thefirst pressure sensor is located remote from a catheter tip of thewithdrawal line, and the controller is configured to determine thevenous pressure of the patient at the catheter tip by compensating forthe pressure head in the withdrawal line between the catheter tip andthe first pressure sensor.

Aspect 45 is a method for reducing one or more plasma constituents inblood of a patient, the method comprising: determining a red blood cellvolume of the blood of the patient; inputting the red blood cell volumeinto a blood filtration system configured to a reduce an amount of oneor more plasma constituents in the blood of the patient; and determininga hematocrit value of the patient, wherein the red blood cell volume isassociated with the hematocrit value of the patient.

In Aspect 46, the subject matter of Aspect 45 optionally includeswherein determining the red blood cell volume of the blood of thepatient includes: injecting a tracer into a blood stream of the patient;and withdrawing one or more blood samples from the blood stream of thepatient.

In Aspect 47, the subject matter of any one or more of Aspects 45-46optionally include wherein determining the red blood cell volume of theblood of the patient includes, controlling a speed of a filtration pumpconfigured to extract a filtrate fluid including one or more plasmaconstituents from a filter by changing a filtration rate from a firstfiltration rate to a second filtration rate; determining a first rate ofchange of an inverse of the hematocrit value of the patientcorresponding to the hematocrit value of the patient at the firstfiltration rate; determining a second rate of change of an inverse ofthe hematocrit value of the patient corresponding to the hematocritvalue of the patient at the second filtration rate; and determining adifference between the first rate of change and the second rate ofchange.

Aspect 48 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: a controllerincluding processing circuitry, wherein the controller is configured to:monitor a hematocrit value of the patient; control a speed of one ormore pumps to adjust a filtration fraction, wherein: the filtrationfraction includes a ratio of a filtration rate to a blood flow ratethrough a filter; the filtration rate includes a rate that one or moreplasma constituents is extracted from the filter, and the blood flowrate includes a rate that blood flows through the filter; compare thehematocrit value to a hematocrit threshold; and maintain the filtrationfraction when the hematocrit value equals the hematocrit threshold.

In Aspect 49, the subject matter of Aspect 48 optionally includeswherein the controller is further configured to control a speed of afiltration pump to adjust the filtration fraction.

In Aspect 50, the subject matter of any one or more of Aspects 48-49optionally include wherein the controller is further configured tocontrol a speed of a blood pump to adjust the filtration fraction.

Aspect 51 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: a controllerincluding processing circuitry, wherein the controller is configured to:monitor a longitudinal filter resistance of a filter configured toreduce an amount of one or more plasma constituents in blood flowingthrough the filter and provide a filtrate fluid including the plasmaconstituents, monitoring the longitudinal filter resistance including:determining a first pressure differential between a blood inlet pressureat an inlet port of the filter and a filtration fluid pressure at afiltration fluid port of the filter; determining a ratio of the firstpressure differential to a blood flow rate of the blood flowing throughthe filter.

In Aspect 52, the subject matter of Aspect 51 optionally includeswherein the controller is further configured to: monitor a transverseresistance of the filter, monitoring the transverse resistanceincluding: determine a second pressure differential between a bloodoutlet pressure at a blood outlet port of the filter and the filtrationfluid pressure; determine a ratio of the second pressure differential toa filtrate flow rate, wherein the filtrate flow rate corresponds to arate that filtrate fluid is removed from the filter.

Aspect 53 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: a filterconfigured to reduce an amount of one or more plasma constituents inblood flowing through the filter and provide a filtrate fluid includingthe plasma constituents, wherein the filter includes: a filter body; ablood inlet port included in the filter body and configured to couplewith a withdrawal line, wherein the withdrawal line is configured tocouple with a catheter and transmit blood from the patient; a bloodoutlet port included in the filter body and configured to couple with aninfusion line, wherein the infusion line is configured to couple withthe catheter and transmit blood to the patient; and a filtrate fluidport included in the filter body and configured to couple with a harvestfluid line, wherein the filter is configured to transmit extractedfiltrate fluid to the filtrate fluid port.

In Aspect 54, the subject matter of Aspect 53 optionally includeswherein the harvesting port is included in the filter body.

In Aspect 55, the subject matter of any one or more of Aspects 53-54optionally include wherein the harvesting port is coupled with the bloodinlet port.

In Aspect 56, the subject matter of any one or more of Aspects 53-55optionally include the catheter configured for insertion into a bloodstream of the patient.

Aspect 57 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: a withdrawalline configured to couple with a catheter and transmit blood from thepatient, the withdrawal line in communication with a first valveconfigured to stop blood flow in the withdrawal line; an infusion lineconfigured to couple with the catheter and transmit blood to thepatient, the infusion line in communication with a second valveconfigured to stop blood flow in the infusion line; a filtration lineconfigured to transmit a filtrate fluid including the one or more plasmaconstituents, the filtration line in communication with a third valveconfigured to stop flow of the filtrate fluid in the filtration line; afilter configured to reduce an amount of the one or more plasmaconstituents in blood flowing through the filter and provide filtratefluid including the plasma constituents, the filter including: a filterbody; a blood inlet port included in the filter body and configured tocouple with a withdrawal line, the blood inlet port in communicationwith a fourth valve configured to stop flow of blood from the bloodinlet port; a blood outlet port included in the filter body andconfigured to couple with the infusion line, the blood outlet port incommunication with a fifth valve configured to stop flow of blood fromthe blood outlet port; and a filtrate fluid port included in the filterbody and configured to couple with the filtration line, wherein thefilter is configured to transmit the filtrate fluid to the filtratefluid port, and the filtrate fluid port is in communication with a sixthvalve configured to stop flow of filtrate fluid from the filtrate fluidport.

In Aspect 58, the subject matter of Aspect 57 optionally includes aharvesting port configured to receive filtrate fluid from the filtratefluid port, the harvesting port in communication with the blood inletport and a seventh valve, the seventh valve configured to stop flow offiltrate fluid or blood from the harvesting port.

Aspect 59 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: a blood pumpin communication with a blood reservoir; a filtration pump configured tocouple with a filter, wherein the filter is configured to reduce anamount of one or more plasma constituents in blood flowing through thefilter and provide a filtrate fluid including the plasma constituents;and a controller including processing circuitry, wherein the controlleris configured to: control the blood pump to operate the blood pump in afirst flow direction to transmit blood from the patient into the bloodreservoir; control the blood pump to transmit blood from the bloodreservoir to the filter, controlling the blood pump to transmit bloodfrom the blood reservoir includes operating the blood pump in a secondflow direction; and control the filtration pump to extract filtrationfluid from the filter and transmit the extracted filtration fluid to afiltrate fluid reservoir.

In Aspect 60, the subject matter of Aspect 59 optionally includes awithdrawal line configured to couple with a catheter, the withdrawalline including at least one check valve, the at least one check valveconfigured to provide unidirectional flow of blood within the withdrawalline.

In Aspect 61, the subject matter of Aspect 60 optionally includeswherein the at least one check valve is configured to prevent blood fromflowing to the catheter when the blood pump transmits blood from theblood reservoir to the filter.

In Aspect 62, the subject matter of any one or more of Aspects 59-61optionally include wherein the blood pump is a peristaltic pump.

Aspect 63 is a blood filtration system for reducing one or more plasmaconstituents in blood of a patient, the system comprising: a controllerincluding processing circuitry, wherein the controller is configured to:control a speed of a blood pump in communication with the controller, tovary a flow rate of blood through a filter to reduce an amount of one ormore plasma constituents in blood flowing through the filter and providea filtrate fluid including the plasma constituents; control the speed ofa harvest pump to vary an extraction rate of filtrate fluid from afiltrate reservoir; determine a venous pressure of the patient, andprovide a notification of the venous pressure of the patient.

Aspect 64 can include or use, or can optionally be combined with anyportion or combination of any portions of any one or more of Aspects 1through 63 to include or use, subject matter that can include means forperforming any one or more of the functions of Aspects 1 through 63, ora machine-readable medium including instructions that, when performed bya machine, cause the machine to perform any one or more of the functionsof Aspects 1 through 63.

The above description includes references to the accompanying drawings,which form a part of the detailed description. The drawings show, by wayof illustration, specific embodiments in which the invention can bepracticed. These embodiments are also referred to herein as “examples.”Such examples can include elements in addition to those shown ordescribed. However, the present inventors also contemplate examples inwhich only those elements shown or described are provided. Moreover, thepresent inventors also contemplate examples using any combination orpermutation of those elements shown or described (or one or more aspectsthereof), either with respect to a particular example (or one or moreaspects thereof), or with respect to other examples (or one or moreaspects thereof) shown or described herein.

In the event of inconsistent usages between this document and anydocuments so incorporated by reference, the usage in this documentcontrols.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, in the followingclaims, the terms “first,” “second,” and “third,” etc. are used merelyas labels, and are not intended to impose numerical requirements ontheir objects.

Geometric terms, such as “parallel”, “perpendicular”, “round”, or“square”, are not intended to require absolute mathematical precision,unless the context indicates otherwise. Instead, such geometric termsallow for variations due to manufacturing or equivalent functions. Forexample, if an element is described as “round” or “generally round,” acomponent that is not precisely circular (e.g., one that is slightlyoblong or is a many-sided polygon) is still encompassed by thisdescription.

Method examples described herein can be machine or computer-implementedat least in part. Some examples can include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods can include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code can include computer readable instructions forperforming various methods. The code can form portions of computerprogram products. Further, in an example, the code can be tangiblystored on one or more volatile, non-transitory, or non-volatile tangiblecomputer-readable media, such as during execution or at other timesExamples of these tangible computer-readable media can include, but arenot limited to, hard disks, removable magnetic disks, removable opticaldisks (e.g., compact disks and digital video disks), magnetic cassettes,memory cards or sticks, random access memories (RAMs), read onlymemories (ROMs), and the like.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) can be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features can be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter canlie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription as examples or embodiments, with each claim standing on itsown as a separate embodiment, and it is contemplated that suchembodiments can be combined with each other in various combinations orpermutations. The scope of the invention should be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1-63. (canceled)
 64. A blood filtration system for reducing one or moreplasma constituents in blood of a patient, the system comprising: avariable-speed blood pump configured to pump blood in a withdrawal line,through a filter, and into an infusion line, wherein: the withdrawalline and the infusion line are configured to couple with a catheter, andthe catheter is configured for insertion into a blood stream of thepatient; a controller including processing circuitry, wherein thecontroller is configured to: determine a withdrawal line resistancecharacteristic of the withdrawal line using a first pressure sensor incommunication with the withdrawal line to measure pressure in thewithdrawal line, the withdrawal line resistance characteristiccorresponding to an amount of resistance to a flow of blood through thewithdrawal line, and wherein determining the withdrawal line resistancecharacteristic includes: determining a blood flow rate through thewithdrawal line using at least one blood flow rate sensor; and dividingthe measured pressure in the withdrawal line by the blood flow ratethrough the withdrawal line; determine an infusion line resistancecharacteristic of the infusion line using a second pressure sensor incommunication with the infusion line to measure pressure in the infusionline, the infusion line resistance characteristic corresponding to anamount of resistance to a flow of blood through the infusion line; andprovide a notification of one or more of the withdrawal line resistancecharacteristic or the infusion line resistance characteristic.
 65. Theblood filtration system of claim 64, wherein the controller isconfigured to: determine a hematocrit value of the patient; determine ahemoconcentration resistance characteristic of the blood according tothe determined hematocrit value of the patient, wherein the withdrawalline resistance characteristic or the infusion line resistancecharacteristic correspond in part to the hemoconcentrationcharacteristic; and determine an occlusion resistance characteristic bysubtracting the hemoconcentration resistance characteristic from thewithdrawal line resistance characteristic or from the infusion lineresistance characteristic.
 66. The blood filtration system of claim 65,wherein the notification of the one or more of the withdrawal lineresistance characteristic or the infusion line resistance characteristicincludes the occlusion resistance characteristic.
 67. The bloodfiltration system of claim 65, wherein the controller is configured toprovide a notification of the occlusion resistance characteristic. 68.The blood filtration system of claim 65, wherein determining thehematocrit value of the patient includes: controlling the speed of theblood pump and setting a flow rate of blood through the filter at afirst blood flow rate; controlling the speed of the blood pump andsetting the flow rate of blood through the filter at a second blood flowrate, wherein the first blood flow rate is different than the secondblood flow rate; and determining the hematocrit at the second blood flowrate.
 69. The blood filtration system of claim 64, wherein thecontroller is configured to: compare the infusion line resistance or thewithdrawal line resistance to a resistance threshold; reduce afiltration rate or increase the blood flow rate if the withdrawal lineresistance or the infusion line resistance exceeds the resistancethreshold.
 70. The blood filtration system of claim 64, wherein thewithdrawal line and the infusion line are configured to be incommunication with the filter, and the filter is configured to reduce anamount of one or more plasma constituents in blood flowing through thefilter and provide a filtrate fluid including the plasma constituents.71. The system of claim 70, wherein the controller is further configuredto: control the speed of a filtration pump to vary the extraction rateof the filtrate fluid from the filter; vary the extraction rate from afirst specified extraction rate; wait for a specified time period;monitor the withdrawal line resistance characteristic or the infusionline resistance characteristic; and provide a notification if theinfusion line resistance characteristic or the withdrawal lineresistance characteristic increases after the specified time period. 72.The system of claim 70, wherein the controller is configured to: vary afiltration rate for reducing the plasma constituents in the blood; waitfor a specified time period; monitor the withdrawal line resistance orthe infusion line resistance; and operate a harvesting pump to extractfiltrate fluid from a filtrate reservoir and inject the filtrate fluidinto an inlet of the filter to dilute the blood flowing through thefilter.
 73. The blood filtration system of claim 64, wherein thecontroller is configured to: determine a venous pressure of the patientby determining a pressure differential between the first pressure sensorand the second pressure sensor; and provide a notification when thepressure differential exceeds a pressure differential threshold.
 74. Theblood filtration system of claim 73, wherein determining the venouspressure of the patient includes compensating for a pressure head in thewithdrawal line.
 75. The blood filtration system of claim 74, furthercomprising a first pressure sensor in communication with the withdrawalline and configured to measure the pressure in the withdrawal line,wherein the first pressure sensor is located remote from a catheter tipof the withdrawal line, and the controller is configured to determinethe venous pressure of the patient at the catheter tip by compensatingfor the pressure head in the withdrawal line between the catheter tipand the first pressure sensor.
 76. The blood filtration system of claim64, wherein determining the infusion line resistance characteristicincludes: determining a blood flow rate through the withdrawal lineusing at least one blood flow rate sensor; and dividing the measuredpressure in the withdrawal line by the blood flow rate through thewithdrawal line.